Elastic substantially linear ethylene polymers

ABSTRACT

Elastic ethylene polymers are disclosed which have processability similar to highly branched low density polyethylene (LDPE), but the strength and toughness of linear low density polyethylene (LLDPE). The polymers have processing indices (PI&#39;s) less than or equal to 70 percent of those of a comparative linear ethylene polymer and a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a traditional linear ethylene polymer at about the same I 2  and M w  /M n . The novel polymers can also have from about 0.01 to about 3 long chain branches/1000 total carbons and have higher low/zero shear viscosity and lower high shear viscosity than comparative linear ethylene polymers. The novel polymers can also be characterized as having a melt flow ratio, I 10  /I 2 , ≧5.63, a molecular weight distribution, M w  /M n , defined by the equation: M w  /M n  ≦(I 10  /I 2 )-4.63, a critical shear stress at onset of gross melt fracture greater than about 4×10 6  dyne/cm 2 , and a single DSC melt peak between -30 C. and 150 C.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of application(s) Ser. No. 08/301,948 filed on Sep.7, 1994, now abandoned which is a continuation-in-part of pending U.S.application Ser. No. 08/044,426 filed Apr. 7, 1993, now U.S. Pat. No.5,380,810 which is a divisional of U.S. application Ser. No. 07/776,130filed Oct. 15, 1991, now U.S. Pat. No. 5,272,236. This application isalso a continuation-in-part of U.S. application Ser. No. 08/166,497filed Dec. 13, 1993, now abandoned which is a divisional of U.S.application Ser. No. 07/939,281 filed Sep. 2, 1992 which is now U.S.Pat. No. 5,278,272.

FIELD OF THE INVENTION

This invention relates to elastic substantially linear ethylene polymershaving improved processability, e.g., low susceptibilty to meltfracture, even under high shear stress conditions. Such substantiallylinear ethylene polymers have a critical shear rate at the onset ofsurface melt fracture substantially higher than, and a processing indexsubstantially less than, that of a linear polyethylene at the samemolecular weight distribution and melt index.

BACKGROUND OF THE INVENTION

Molecular weight distribution (MWD), or polydispersity, is a well knownvariable in polymers. The molecular weight distribution, sometimesdescribed as the ratio of weight average molecular weight (M_(w)) tonumber average molecular weight (M_(n)) (i.e., M_(w) /M_(n)) can bemeasured directly, e.g., by gel permeation chromatography techniques, ormore routinely, by measuring I₁₀ /I₂ ratio, as described in ASTM D-1238.For linear polyolefins, especially linear polyethylene, it is well knownthat as M_(w) /M_(n) increases, I₁₀ /I₂ also increases.

John Dealy in "Melt Rheology and Its Role in Plastics Processing" (VanNostrand Reinhold, 1990) page 597 discloses that ASTM D-1238 is employedwith different loads in order to obtain an estimate of the shear ratedependence of melt viscosity, which is sensitive to weight averagemolecular weight (M_(w)) and number average molecular weight (M_(n)).

Bersted in Journal of Applied Polymer Science Vol. 19, page 2167-2177(1975) theorized the relationship between molecular weight distributionand steady shear melt viscosity for linear polymer systems. He alsoshowed that the broader MWD material exhibits a higher shear rate orshear stress dependency.

Ramamurthy in Journal of Rheology, 30(2), 337-357 (1986), and Moynihan,Baird and Ramanathan in Journal of Non-Newtonian Fluid Mechanics, 36,255-263 (1990), both disclose that the onset of sharkskin (i.e., surfacemelt fracture) for linear low density polyethylene (LLDPE) occurs at anapparent shear stress of 1-1.4×10⁶ dyne/cm², which was observed to becoincident with the change in slope of the flow curve. Ramamurthy alsodiscloses that the of surface melt fracture or of gross melt fracturefor high pressure low density polyethylene (HP-LDPE) occurs at anapparent shear stress of about 0.13 MPa (1.3×10⁶ dyne/cm²). Ramamurthyalso discloses that "the corresponding shear stresses (0.14 and 0.43MPa) for linear polyethylenes are widely separated." However, theseLLDPE resins are linear resins, and are believed to be those made byUnion Carbide in their UNIPOL process (which uses conventionalZiegler-Natta catalysis which results in a heterogeneous comonomerdistribution). The LLDPE is reported in Tables I and II to have a broadM_(w) /M_(n) of 3.9. The melt fracture tests conducted by Ramamurthywere in the temperature range of 190 to 220 C. Furthermore, Ramamurthyreports that the onset of both surface and gross melt fracture (forLLDPE resins) are " . . . essentially independent of MI (or molecularweight), melt temperature, die diameter (0.5-2.5 mm), dielength/diameter ratio (2-20), and the die entry angle (included angle:60-180 degrees)."

Kalika and Denn in Journal of Rheology, 31, 815-834 (1987) confirmed thesurface defects or sharkskin phenomena for LLDPE, but the results oftheir work determined a critical shear stress at onset of surface meltfracture of 0.26 MPa, significantly higher than that found byRamnamurthy and Moynihan et al. Kalika and Denn also report that theonset of gross melt fracture occurs at 0.43 MPa which is consistent withthat reported by Ramamurthy. The LLDPE resin tested by Kalika and Dennwas an antioxidant-modified (of unknown type) UNIPOL LLDPE having abroad M_(w) /M_(n) of 3.9. Kalika and Denn performed their melt fracturetests at 215 C. However, Kalika and Denn seemingly differ withRamamurthy in the effects of their L/D of the rheometer capillary.Kalika and Denn tested their LLDPE at L/D's of 33.2, 66.2, 100.1, and133.1 (see Table 1 and FIGS. 5 and 6).

International Patent Application (Publication No. WO 90/03414) publishedApr. 5, 1990 to Exxon Chemical Company, discloses linear ethyleneinterpolymer blends with narrow molecular weight distribution and narrowshort chain branching distributions (SCBDs). The melt processibility ofthe interpolymer blends is controlled by blending different molecularweight interpolymers having different narrow molecular weightdistributions and different SCBDs.

Exxon Chemical Company, in the Preprints of Polyolefins VIIInternational Conference, page 45-66, Feb. 24-27 1991, disclose that thenarrow molecular weight distribution (NMWD) resins produced by theirEXXPOL™ technology have higher melt viscosity and lower melt strengththan conventional Ziegler resins at the same melt index. In a recentpublication, Exxon Chemical Company has also taught that NMWD polymersmade using a single site catalyst create the potential for melt fracture("New Specialty Linear Polymers (SLP) For Power Cables," by MonicaHendewerk and Lawrence Spenadel, presented at IEEE meeting in Dallas,Tex., September, 1991). In a similar vein, in "A New Family of LinearEthylene Polymers Provides Enhanced Sealing Performance" by Dirk G. F.Van der Sanden and Richard W. Halle, (February 1992 Tappi Journal),Exxon Chemical Company has also taught that the molecular weightdistribution of a polymer is described by the polymers melt index ratio(i.e., I₁₀ /I₂ and that their new narrow molecular weight distributionpolymers made using a single site catalyst are "linear backbone resinscontaining no functional or long chain branches."

U.S. Pat. No. 5,218,071 (Canadian patent application 2,008,315-A) toMitsui Petrochemical Industries, Ltd., teaches ethylene copolymerscomposed of structural units (a) derived from ethylene and structuralunits (b) derived from alpha-olefins of 3-20 carbons atoms, saidethylene copolymers having A! a density of 0.85-0.92 g/cm³, B! anintrinsic viscosity as measured in decalin at 135 C. of 0.1-10 dl/g, C!a ratio (M_(w) /M_(n)) of a weight average molecular weight (M_(w)) to anumber average molecular weight (M_(n)) as measured by GPC of 1.2-4, andD! a ratio (MFR₁₀ /MFR₂) of MFR₁₀ under a load of 10 kg to MFR₂ under aload of 2.16 kg at 190 C. of 8-50, and being narrow in molecular weightdistribution and excellent in flowability. However, the ethylenecopolymers of U.S. Pat. No. '071 are made with a catalysis systemcomposed of methylalumninoxane and ethylenebis(indenyl)hafniumdichloride (derived from HfCl₄ containing 0.78% by weight of zirconiumatoms as contaminates). It is well known that mixed metal atom catalystspecies (such as hafnium and zirconium in U.S. Pat. No. '071)polymerizes copolymer blends, which are evidence by multiple meltingpeaks. Such copolymer blends therefore are not homogeneous in terms oftheir branching distribution.

WO 85/04664 to BP Chemicals Ltd. teaches a process for thethermo-mechanical treatment of copolymers of ethylene and higheralpha-olefins of the linear low density polyethylene type with at leastone or more organic peroxides to produce copolymers that areparticularly well suited for extrusion or blow-molding into hollowbodies, sheathing, and the like. These treated copolymers show anincreased flow parameter (I₂₁,/I₂) without significantly increasing theM_(w) /M_(n). However, the novel polymers of the present invention havelong chained branching and obtained this desirable result without theneed of a peroxide treatment.

U.S. Pat. No. 5,096,867 discloses various ethylene polymers made using asingle site catalyst in combinations with methyl aluminoxane. Thesepolymers, in particular Example 47, have extremely high levels ofalumninum resulting from catalyst residue. When these aluminum residuesare removed from the polymer, the polymer exhibits gross melt fractureat a critical shear stress of less than 4×10⁶ dyne/cm².

All of the foregoing patents, applications, and articles are hereinincorporated by reference.

Previously known narrow molecular weight distribution linear polymersdisadvantageously possessed low shear sensitivity or low I₁₀ /I₂ value,which limits the extrudability of such polymers. Additionally, suchpolymers possessed low melt elasticity, causing problems in meltfabrication such as film forming processes or blow molding processes(e.g., sustaining a bubble in the blown film process, or sag in the blowmolding process etc.). Finally, such resins also experienced meltfracture surface properties at relatively low extrusion rates therebyprocessing unacceptably.

SUMMARY OF THE INVENTION

A new class of homogeneous ethylene polymers have now been discoveredwhich have long chain branching and unusual but desirable bulkproperties. These new polymers include both homopolymers of ethylene andinterpolymers of ethylene and at least one alpha-olefin. Both the homo-and interpolymers have long chain branching, but the interpolymers haveshort chain branching in addition to the long chain branching. The shortchain branches are the residue of the alpha-olefins that areincorporated into the polymer backbone or in other words, the shortchain branches are that part of the alpha-olefin not incorporated intothe polymer backbone. The length of the short chain branches is twocarbon atoms less than the length of the alpha-olefin comonomer. Theshort chain branches are randomly, i.e. uniformily, distributedthroughout the polymer as opposed to heterogeneously branchedethylene/alpha-olefin interpolymers such as conventional Zeigler LLDPE.

These novel ethylene polymers have a shear thinning and ease ofprocessability similar to highly branched low density polyethylene(LDPE), but with the strength and toughness of linear low densitypolyethylene (LLDPE). These novel ethylene polymers can also becharacterized as "substantially linear" polymers, whereby the bulkpolymer has an average of up to about 3 long chain branches/1000 totalcarbons or in other words, at least some of the polymer chains have longchain branching. The novel substantially linear ethylene polymers aredistinctly different from traditional Ziegler polymerized heterogeneouspolymers (e.g., LLDPE) and are also different from traditional freeradical/high pressure polymerized LDPE. Surprisingly, the novelsubstantially linear ethylene polymers are also different from linearhomogeneous ethylene polymers having a uniform comonomer distribution,especially with regard to processability.

These novel ethylene polymers, especially those with a density greaterthan or equal to about 0.9 g/cm³ are characterized as having:

a) a melt flow ratio, I₁₀ /I₂, ≧5.63,

b) a molecular weight distribution, M_(w) /M_(n), defined by theequation:

    M.sub.w /M.sub.n ≦(I.sub.10 /I.sub.2)-4.63,

c) a critical shear stress at onset of gross melt fracture greater thanabout 4×10⁶ dyne/cm², and

d) a single melt peak as determined by differential scanning calorimetry(DSC) between -30 and 150 C.

The novel ethylene polymers can also be characterized as having:

a) a melt flow ratio, I₁₀ /I₂, ≧5.63,

b) a molecular weight distribution, M_(w) /M_(n), defined by theequation:

    M.sub.w /M.sub.n ≦(I.sub.10 /I.sub.2)-4.63,

c) a critical shear rate at onset of surface melt fracture at least 50percent greater than the critical shear rate at the onset of surfacemelt fracture of a linear ethylene polymer with an I₂, M_(w) /M_(n), anddensity each within ten percent of the novel ethylene polymer, and

d) a single melt peak as determined by differential scanning calorimetry(DSC) between -30 and 150 C.

In another aspect, the novel ethylene polymers, especially those havinga density greater than or equal to about 0.9 g/cm³, are characterized ashaving:

a) a melt flow ratio, I₁₀ /I₂,≦5.63, and

b) a molecular weight distribution, M_(w) /M_(n) of from about 1.5 toabout 2.5,

c) a critical shear stress at onset of gross melt fracture greater thanabout 4×10⁶ dyne/cm², and

d) a single melt peak as determined by differential scanning calorimetry(DSC) between -30 and 150 C.

In still another aspect, the novel ethylene polymers are characterizedas having:

a) a melt flow ratio, I₁₀ /I₂,≦5.63,

b) a molecular weight distribution, M_(w) /M_(n) of from about 1.5 toabout 2.5,

c) a critical shear rate at onset of surface melt fracture of at least50 percent greater than the critical shear rate at the onset of surfacemelt fracture of a linear ethylene polymer with an I₂, M_(w) /M_(n), anddensity each within ten percent of the novel ethylene polymer, and

d) a single melt peak as determined by differential scanning calorimetry(DSC) between -30 and 150 C.

The substantially linear ethylene polymers can also be characterized ashaving a critical shear rate at onset of surface melt fracture of atleast 50 percent greater than the critical shear rate at the onset ofsurface melt fracture of a linear ethylene polymer having an I₂, M_(w)/M_(n) and density each within ten percent of the substantially linearethylene polymer.

In still another aspect the novel polymer can be characterized as asubstantially linear ethylene bulk polymer having:

(a) and average of about 0.01 to about 3 long chain branches/1000 totalcarbons,

(b) a critical shear stress at onset of gross melt fracture of greaterthan about 4×10⁶ dyne/cm², and

(c) a single DSC melt peak between -30 and 150 C.

The substantially linear ethylene bulk polymer can also be characterizedas having:

(a) an average of about 0.01 to about 3 long chain branches/1000 totalcarbons,

(b) a critical shear rate at onset of surface melt fracture of at least50 percent greater than the critical shear rate at the onset of surfacemelt fracture of a linear ethylene polymer having an I₂, M_(w) /M_(n)and density each within ten percent of the substantially linear ethylenebulk polymer, and

(c) a single DSC melt peak between -30 and 150 C.

In still another aspect, the ethylene polymer can be characterized as asubstantially linear ethylene bulk polymer having:

(a) and average of about 0.01 to about 3 long chain branches/1000 totalcarbons,

(b) a melt flow ratio, I₁₀ /I₂, ≧5.63,

(c) a molecular weight distribution, M_(w) /M_(n), from about 1.5 toabout 2.5, and

(d) a single DSC melt peak between -30 and 150 C.

The novel ethylene polymers, especially the substantially linearethylene polymers, also have a processing index (PI) less than or equalto about 70 percent of the PI of a linear ethylene polymer at about thesame I₂, M_(w) /M_(n), and density each within ten percent of the novelethylene polymer.

Compositions comprising the novel ethylene polymer and at least oneother natural or synthetic polymer are also within the scope of theinvention.

Elastic substantially linear ethylene polymers comprising ethylenehomopolymers or an interpolymer of ethylene with at least one C₃ -C₂₀alpha-olefin copolymers are especially preferred.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a polymerization processsuitable for making the polymers of the present invention.

FIG. 2 plots data describing the relationship between I₁₀ /I₂ and M_(w)/M_(n) for two examples of the invention, and for some comparativeexamples.

FIG. 3 plots the shear stress versus shear rate for an Example of theinvention and for a Comparative Example, described herein.

FIG. 4 plots the shear stress versus shear rate for an Example of theinvention and for a Comparative Example, described herein.

FIG. 5 plots the heat seal strength versus heat seal temperature of filmmade from Examples of the invention, and for Comparative Examples,described herein.

FIG. 6 graphically displays dynamic shear viscosity data for an elasticsubstantially linear ethylene polymer of the present invention and for acomparative linear polymer made using single site catalyst technology.

FIG. 7 graphically displays I₁₀ /I₂ ratio as a function of ethyleneconcentration in the polymerization reactor for ethylene/propenesubstantially linear copolymers of the invention.

FIG. 8 graphically displays the melting curves for a comparative polymermade according to U.S. Pat. No. 5,218,071 (Mitsui).

FIG. 9 graphically displays the structural characteristics of atraditional heterogeneous Ziegler polymerized LLDPE copolymers, a highlybranched high pressure-free radical LDPE, and a novel substantiallylinear ethylene/alpha-olefin copolymer of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The term "linear" as used herein means that the ethylene polymer doesnot have long chain branching. That is, the polymer chains comprisingthe bulk linear ethylene polymer have an absence of long chainbranching, as for example the traditional linear low densitypolyethylene polymers or linear high density polyethylene polymers madeusing Ziegler polymerization processes (e.g., U.S. Pat. No. 4,076,698(Anderson et al.)), sometimes called heterogeneous polymers. The term"linear" does not refer to bulk high pressure branched polyethylene,ethylene/vinyl acetate copolymers, or ethylene/vinyl alcohol copolymerswhich are known to those skilled in the art to have numerous long chainbranches. The term "linear" also refers to polymers made using uniformbranching distribution polymerization processes, sometimes calledhomogeneous polymers, including narrow MWD (e.g. about 2) made usingsingle site catalysts. Such uniformly branched or homogeneous polymersinclude those made as described in U.S. Pat. No. 3,645,992 (Elston) andthose made using so-called single site catalysts in a batch reactor,having relatively high ethylene concentrations (as described in U.S.Pat. No. 5,026,798 (Canich) or in U.S. Pat. No. 5,055,438 (Canich)) orthose made using constrained geometry catalysts in a batch reactor alsohaving relatively high olefin concentrations (as described in U.S. Pat.No. 5,064,802 (Stevens et al.) or in EP 0 416 815 A2 (Stevens et al.)).The uniformly branched homogeneous polymers are those polymers in whichthe comonomer is randomly distributed within a given interpolymermolecule or chain, and wherein substantially all of the interpolymermolecules have the same ethylene/comonomer ratio within thatinterpolymer, but these polymers too have an absence of long chainbranching, as, for example, Exxon Chemical has taught in their February1992 Tappi Journal paper. For example, FIG. 9 shows the structuraldifferences among conventional heterogeneously branched LLDPE,homogeneously branched linear LLDPE, highly branched high pressure, freeradical LDPE, and the homogeneously branched substantially linearethylene polymers of the present invention.

The term "substantially linear" as used means that the bulk polymer issubstituted, on average, with about 0.01 long chain branches/1000 totalcarbons (including both backbone and branch carbons) to about 3 longchain branches/1000 total carbons. Preferred polymers are substitutedwith about 0.01 long chain branches/1000 total carbons to about 1 longchain branches/1000 total carbons, more preferably from about 0.05 longchain branches/1000 total carbons to about 1 long chain branched/1000total carbons, and especially from about 0.3 long chain branches/1000total carbons to about 1 long chain branches/1000 total carbons.

As used herein, the term "backbone" refers to a discrete molecule, andthe term "polymer" or "bulk polymer" refers in the conventional sense tothe polymer as formed in a reactor. For the polymer to be a"substantially linear" polymer, the polymer must have at least enoughmolecules with long chain branching such that the average long chainbranching in the bulk polymer is at least an average of about 0.01/1000total carbons.

The term "bulk polymer" means the polymer which results from thepolymerization process and, for the substantially linear polymers,includes molecules having both an absence of long chain branching, aswell as molecules having long chain branching. Thus a "bulk polymer"includes all molecules formed during polymerization. It is understoodthat, for the substantially linear polymers, not all molecules have longchain branching, but a sufficient amount do such that the average longchain branching content of the bulk polymer positively affects the meltrheology (i.e., the melt fracture properties).

Long chain branching (LCB) is defined herein as a chain length of atleast one (1) carbon less than the number of carbons in the comonomer,whereas short chain branching (SCB) is defined herein as a chain lengthof the same number of carbons in the residue of the comonomer after itis incorporated into the polymer molecule backbone. For example, anethylene/1-octene substantially linear polymer has backbones with longchain branches of at least seven (7) carbons in length, but it also hasshort chain branches of only six (6) carbons in length.

Long chain branching can be distinguished from short chain branching byusing ¹³ C nuclear magnetic resonance (NMR) spectroscopy and to alimited extent, e.g. for ethylene homopolymer it can be quantified usingthe method of Randall (Rev. Macromol. Chem. Phys., C29 (2&3), p.285-297), the disclosure of which is incorporated herein by reference.However as a practical matter, current ¹³ C nuclear magnetic resonancespectroscopy cannot determine the length of a long chain branch inexcess of about six (6) carbon atoms and as such, this analyticaltechnique cannot distinguish between a seven (7) carbon branch and aseventy (70) carbon branch. The long chain branch can be as long asabout the same length as the length of the polymer backbone.

U.S. Pat. No. 4,500,648, incorporated herein by reference, teaches thatlong chain branching frequeny (LCB) can be represented by the equationLCB=b/M_(w) wherein b is the weight average number of long chainbranches per molecule and M_(w) is the weight average molecular weight.The molecular weight averages and the long chain branchingcharacteristics are determined by gel permeation chromatography andintrinsic viscosity methods.

Similar to the traditional homogeneous polymers, the substantiallylinear ethylene/alpha-olefin copolymers of the invention have only asingle melting point, as opposed to traditional Ziegler polymerizedheterogeneous linear ethylene/alpha-olefin copolymers which have two ormore melting points (determined using differential scanning calorimetry(DSC)). Ethylene polymers of this invention are also characterized by asingle DSC melting peak between -30 and 150 C. However, those polymershaving a density of about 0.875 g/cm³ to about 0.91 g/cm³, the singlemelt peak may show, depending on equipment sensitivity, a "shoulder" ora "hump" on the low side of the melting peak (i.e. below the meltingpoint) that constitutes less than 12 percent, typically, less than 9percent, more typically less than 6 percent of the total heat of fusionof the polymer. This artifact is due to intrapolymer chain variations,and it is discerned on the basis of the slope of the single melting peakvarying montonically through the melting region of the artifact. Suchartifact occurs within 34 C., typically within 27 C., and more typicallywithin 20 C. of the melting point of the single melting peak. The singlemelting peak is determined using a differential scanning calorimeterstandardized with indium and deionized water. The method involves about5-7 mg sample sizes, a "first heat" to about 150 C. which is held for 4minutes, a cool down at 10/min. to -30 C. which is held for 3 minutes,and heat up at 10 C./min. to 150 C. for the "second heat" heat flow vs.temperature curve. Total heat of fusion of the polymer is calculatedfrom the area under the curve. The heat of fusion attributable to thisartifact, if present, can be determined using an analytical balance andweight-percent calculations.

FIG. 8 displays the melting curves for a polymer of the invention andfor a comparative polymer as described in U.S. Pat. No. 5,218,071(Mitsui). Note that the comparative polymer has two melting peaks (thehigh melting peak with a shoulder on its high side, i.e. above thesecond melting point), and this is indicative of the presence of twodistinct polymers (as opposed to the melting curve of the inventionpolymer having only a single melting peak).

The SCBDI (Short Chain Branch Distribution Index) or CDBI (CompositionDistribution Branch Index) is defined, as the weight percent of thepolymer molecules having a comonomer content within 50 percent of themedian total molar comonomer content The CDBI of a polymer is readilycalculated from data obtained from techniques known in the art, such as,for example, temperature rising elution fractionation (abbreviatedherein as "TREF") as described, for example, in Wild et al, Journal ofPolymer Science, Poly. Phys. Ed., Vol. 20, p. 441 (1982), or asdescribed in U.S. Pat. No. 4,798,081. The SCBDI or CDBI for thesubstantially linear ethylene polymers of the present invention istypically greater than about 30 percent, preferably greater than about50 percent, more preferably greater than about 80 percent, and mostpreferably greater than about 90 percent.

"Melt tension" is measured by a specially designed pulley transducer inconjunction with the melt indexer. Melt tension is the load that theextrudate or filament exerts while passing over the pulley onto a twoinch drum that is rotating at the standard speed of 30 rpm. The melttension measurement is similar to the "Melt Tension Tester" made byToyoseiki and is described by John Dealy in "Rheometers for MoltenPlastics", published by Van Nostrand Reinhold Co. (1982) on page250-251. The melt tension of these new polymers is also surprisinglygood, e.g., as high as about 2 grams or more. For the novelsubstantially linear ethylene interpolymers of this invention,especially those having a very narrow molecular weight distribution(i.e., M_(w) /M_(n) from 1.5 to 2.5), the melt tension is typically atleast about 5 percent, and can be as much as about 60 percent, greaterthan the melt tension of a conventional linear ethylene interpolymerhaving a melt index, polydispersity and density each within ten percentof the substantially linear ethylene polymer.

A unique characteristic of the presently claimed polymers is a highlyunexpected flow property where the I₁₀ /I₂ value is essentiallyindependent of polydispersity index (i.e. M_(w) /M_(n)). This iscontrasted with conventional Ziegler polymerized heterogeneouspolyethylene resins and with conventional single site catalystpolymerized homogeneous polyethylene resins having Theologicalproperties such that as the polydispersity index increases, the I₁₀ /I₂value also increases.

The density of the neat ethylene or substantially linear ethylenepolymers of this invention, i.e. polymers without inorganic fillers andnot containing in excess of 20 ppm aluminum from catalyst residue, ismeasured in accordance with ASTM D-792. The ethylene or substantiallylinear ethylene polymers are crystalline and/or semi-crystallinepolymers, are normally solid at room temperature, and are pelletizableat ambient conditions or at temperatures induced by cooled water. Forexample, a novel substantially linear ethylene/ioctene copolymer havinga density of 0.865 g/cm³ has about 10% crystallinity at roomtemperature. The minimum density is typically at least about 0.865g/cm³, preferably at least about 0.870 g/cm³, and more preferably atleast about 0.900 g/cm³. The maximum density typically does not exceedabout 0.970 g/cm³, preferably it does not exceed about 0.940 g/cm³, andmore preferably it does not exceed about 0.92 g/cm³.

The molecular weight of the ethylene or ethylene/alpha-olefinsubstantially linear ethylene polymers in the present invention isconveniently indicated using a melt index measurement according to ASTMD-1238, Condition 190 C./2.16 kg (formally known as "Condition (E)" andalso known as I₂). Melt index is inversely proportional to the molecularweight of the polymer. Thus, the higher the molecular weight, the lowerthe melt index, although the relationship is not linear. The melt indexfor the ethylene or ethylene/alpha-olefin substantially linear ethylenepolymers used herein is generally from about 0.01 grams/10 minutes (g/10min) to about 1000 g/10 min, preferably from about 0.01 g/10 min toabout 100 g/10 min, and especially from about 0.01 g/10 min to about 10g/10 min.

Another measurement useful in characterizing the molecular weight of thesubstantially linear ethylene polymers is conveniently indicated using amelt index measurement according to ASTM D-1238, Condition 190 C./10 kg(formerly known as "Condition (N)" and also known as I₁₀). The ratio ofthese two melt index terms is the melt flow ratio and is designated asI₁₀ /I₂. For the substantially linear ethylene/alpha-olefin polymers ofthe invention, the I₁₀ /I₂ ratio indicates the degree of long chainbranching, ie., the higher the I₁₀ /I₂ ratio, the more long chainbranching in the polymer. Generally, the I₁₀ /I₂ ratio of thesubstantially linear ethylene/alpha-olefin polymers is at least about5.63, preferably at least about 7, especially at least about 8, mostespecially at least about 9 or above. The only limitations on themaximum I₁₀ /I₂ ratio are practical considerations such as economics,polymerization kinetics, etc., but typically the maximum I₁₀ /I₂ ratiodoes not exceed about 20, and preferably it does not exceed about 15.

Antioxidants (e.g., hindered phenolics (e.g., Irganox® 1010 made by CibaGeigy Corp.), phosphites (e.g., Irgafos® 168 made by Ciba Geigy Corp.)),are preferably added to protect the polymer from degradation duringthermal processing steps such as pelletization, molding, extrusion, andcharacterization methods. Other additives to serve special functionalneeds include cling additives, e.g. PIB, antiblocks, antislips,pigments, fillers. In-process additives, e.g. calcium stearate, water,etc., may also be used for other purposes such as for the deactivationof residual catalyst. However, peroxide need not be added to the novelpolymers in order for the polymers to exhibit an I₁₀ /I₂ independent ofthe MWD and the melt fracture properties.

Molecular Weight Distribution Determination

The whole interpolymer product samples and the individual interpolymersamples are analyzed by gel permeation chromatography (GPC) on a Waters150 C. high temperature chromatographic unit equipped with three linearmixed porosity bed columns (available from Polymer Laboratories),operating at a system temperature of 140 C. The solvent is1,2,4-trichlorobenzene, from which 0.3 percent by weight solutions ofthe samples are prepared for injection. The flow rate is 1.0milliliters/minute and the injection size is 200 microliters.

The molecular weight determination is deduced by using narrow molecularweight distribution polystyrene standards (from Polymer Laboratories) inconjunction with their elution volumes. The equivalent polyethylenemolecular weights are determined by using appropriate Mark-Houwinkcoefficients for polyethylene and polystyrene (as described by Williamsand Ward in Journal of Polymer Science, Polymer Letters, Vol. 6, (621)1968) to derive the following equation:

    M.sub.polyethylene =a*(M.sub.polystryrene).sup.b.

In this equation, a=0.4316 and b=1.0 for polyethylene and polystyrene in1,2,4-trichlorobenzene. Weight average molecular weight, M_(w), iscalculated in the usual manner according to the following formula: M_(w)=εw_(i) *M_(i), where w_(i) and M_(i) are the weight fraction andmolecular weight, respectively, of the i^(th) fraction eluting from theGPC column.

The molecular weight distribution (M_(w) /M_(n)) for the substantiallylinear ethylene polymers of the invention is generally less than about5, preferably from about 1.5 to about 2.5, and especially from about 1.7to about 2.3.

Processing Index Determination

The "Theological processing index" (PI) is the apparent viscosity (inkpoise) of a polymer and is measured by a gas extrusion rheometer (GER).The GER is described by M. Shida, R. N. Shroff and L. V. Cancio inPolym. Eng. Sci., Vol. 17, no. 11, p. 770 (1977), and in "Rheometers forMolten Plastics" by John Dealy, published by Van Nostrand Reinhold Co.(1982) on page 97-99, the disclosures of both of which are incorporatedin their entirety herein by reference. The processing index is measuredat a temperature of 190 C., at nitrogen pressure of 2500 psig using a0.0296 inch (752 micrometers) diameter (preferably 0.0143 inch diameterdie for high flow polymers, e.g. 50-100 melt index or greater), 20:1 L/Ddie having an entrance angle of 180 degrees. The GER processing index iscalculated in millipoise units from the following equation:

    PI=2.15×10.sup.6 dyne/cm.sup.2 /(1000×shear rate),

where: 2.15×10⁶ dyne/cm² is the shear stress at 2500 psi, and the shearrate is the shear rate at the wall as represented by the followingequation:

32 Q'/(60 sec/min)(0.745)(Diameter×2.54 cm/in)³, where:

Q' is the extrusion rate (gms/min),

0.745 is the melt density of polyethylene (gm/cm³), and

Diameter is the orifice diameter of the capillary (inches).

The PI is the apparent viscosity of a material measured at apparentshear stress of 2.15×10⁶ dyne/cm².

For the substantially linear ethylene polymers (or ethylene/alpha-olefincopolymers or interpolymers), the PI is less than or equal to 70 percentof that of a conventional linear ethylene polymer (orethylene/alpha-olefin copolymer or interpolymer) having an I₂, M_(w)/M_(n) and density each within ten percent of the substantially linearethylene polymer.

An apparent shear stress vs. apparent shear rate plot is used toidentify the melt fracture phenomena over a range of nitrogen pressuresfrom 5250 to 500 psig using the die or GER test apparatus previouslydescribed. According to Ramamurthy in Journal of Rheology, 30(2),337-357, 1986, above a certain critical flow rate, the observedextrudate irregularities may be broadly classified into two main types:surface melt fracture and gross melt fracture.

Surface melt fracture occurs under apparently steady flow conditions andranges in detail from loss of specular gloss to the more severe form of"sharkskin". In this disclosure, the onset of surface melt fracture ischaracterized at the beginning of losing extrudate gloss at which thesurface roughness of extrudate can only be detected by 40×magnification. The critical shear rate at onset of surface melt fracturefor the substantially linear ethylene polymers is at least 50 percentgreater than the critical shear rate at the onset of surface meltfracture of a linear ethylene polymer having about the same I₂ and M_(w)/M_(n). Preferably, the critical shear stress at onset of surface meltfracture for the substantially linear ethylene polymers of the inventionis greater than about 2.8×10⁶ dyne/cm².

Gross melt fracture occurs at unsteady flow conditions and ranges indetail from regular (alternating rough and smooth, helical, etc.) torandom distortions. For commercial acceptability, (e.g., in blown filmproducts), surface defects should be minimal, if not absent. Thecritical shear rate at onset of surface melt fracture (OSMF) andcritical shear stress at onset of gross melt fracture (OGMF) will beused herein based on the changes of surface roughness and configurationsof the extrudates extruded by a GER. For the substantially linearethylene polymers of the invention, the critical shear stress at onsetof gross melt fracture is preferably greater than about 4×10⁶ dyne/cm².

For the processing index determination and for the GER melt fracturedetermination, the novel ethylene or substantially linear ethylenecopolymers are tested without inorganic fillers, and they do not havemore than 20 ppm aluminum catalyst residue. Preferably, however, for theprocessing index and melt fracture tests, the novel ethylene polymersand substantially linear ethylene copolymers do contain antioxidantssuch as phenols, hindered phenols, phosphites or phosphonites,preferably a combination of a phenol or hindered phenol and a phosphiteor a phosphonite.

The Constrained Geometry Catalyst

Suitable constrained geometry catalysts for use herein preferablyinclude constrained geometry catalysts as disclosed in U.S. applicationSer. No. 545,403, filed Jul. 3, 1990; Ser. No. 758,654, filed Sep. 12,1991 (now U.S. Pat. No. 5,132,380); Ser. No. 758,660, filed Sep. 12,1991, now abandoned; and Ser. No. 720,041, filed Jun. 24, 1991, nowabandoned. The monocyclopentadienyl transition metal olefinpolymerization catalysts taught in U.S. Pat. No. 5,026,798 which isincorporated herein by reference, are also believed to be suitable foruse in preparing the polymers of the present invention, so long as thepolymerization conditions substantially conform to those.

The foregoing catalysts may be further described as comprising a metalcoordination complex comprising a metal of groups 3-10 or the Lanthanideseries of the Periodic Table of the Elements and a delocalized pi-bondedmoiety substituted with a constrain-inducing moiety, said complex havinga constrained geometry about the metal atom such that the angle at themetal between the centroid of the delocalized, substituted pi-bondedmoiety and the center of at least one remaining substituent is less thansuch angle in a similar complex containing a similar pi-bonded moietylacking in such constrain-inducing substituent, and provided furtherthat for such complexes comprising more than one delocalized,substituted pi-bonded moiety, only one thereof for each metal atom ofthe complex is a cyclic, delocalized, substituted pi-bonded moiety. Thecatalyst further comprises an activating cocatalyst.

Preferred catalyst complexes correspond to the formula: ##STR1##wherein: M is a metal of group 3-10, or the Lanthanide series of thePeriodic Table of the Elements;

Cp* is a cyclopentadienyl or substituted cyclopentadienyl group bound inan eta⁵ bonding mode to M;

Z is a moiety comprising boron, or a member of group 14 of the PeriodicTable of the Elements, and optionally sulfur or oxygen, said moietyhaving up to 20 non-hydrogen atoms, and optionally Cp* and Z togetherform a fused ring system;

X independently each occurrence is an anionic ligand group or neutralLewis base ligand group having up to 30 non-hydrogen atoms;

n is 0, 1, 2, 3, or 4 and is 2 less than the valence of M; and

Y is an anionic or nonanionic ligand group bonded to Z and M comprisingnitrogen, phosphorus, oxygen or sulfur and having up to 20 non-hydrogenatoms, optionally Y and Z together form a fused ring system.

More preferably still, such complexes correspond to the formula:##STR2## wherein: R' each occurrence is independently selected from thegroup consisting of hydrogen, alkyl, aryl silyl, germyl, cyano, halo andcombinations thereof having up to 20 non-hydrogen atoms;

X each occurrence independently is selected from the group consisting ofhydride, halo, alkyl, aryl, silyl, germyl, aryloxy, alkoxy, amide,siloxy, neutral Lewis base ligands and combinations thereof having up to20 non-hydrogen atoms;

Y is --O--, --S--, --NR*--, --PR*--, or a neutral two electron donorligand selected from the group consisting of OR*, SR*, NR*₂ or PR*₂ ;

M is as previously defined; and

Z is SiR*₂, CR*₂, SR*₂ SiR*₂, CR*₂ CR*₂, CR*═CR*, CR*₂ SiR*₂, GeR*₂,BR*, BR*₂ ;

wherein

R* each occurrence is independently selected from the group consistingof hydrogen, alkyl, aryl, silyl, halogenated alkyl, halogenated arylgroups having up to 20 non-hydrogen atoms, and mixtures thereof, or twoor more R* groups from Y, Z, or both Y and Z form a fused ring system;and n is 1 or 2.

It should be noted that whereas formula I and the following formulasindicate a cyclic structure for the catalysts, when Y is a neutral twoelectron donor ligand, the bond between M and Y is more accuratelyreferred to as a coordinate-covalent bond. Also, it should be noted thatthe complex may exist as a dimer or higher oligomer.

Further preferably, at least one of R', Z, or R* is an electron donatingmoiety. Thus, highly preferably Y is a nitrogen or phosphorus containinggroup corresponding to the formula --N(R")-- or --P(R")--, wherein R" isC₁₋₁₀ alkyl or aryl, i.e., an amido or phosphido group.

Most highly preferred complex compounds are amidosilane- oramidoalkanediyl-compounds corresponding to the formula: ##STR3##wherein: M is titanium, zirconium or hafnium, bound in an eta⁵ bondingmode to the cyclopentadienyl group;

R' each occurrence is independently selected from the group consistingof hydrogen, silyl, alkyl, aryl and combinations thereof having up to 10carbon or silicon atoms;

E is silicon or carbon;

X independently each occurrence is hydride, halo, alkyl, aryl, aryloxyor alkoxy of up to 10 carbons;

m is 1 or 2; and

n is 1 or 2.

Examples of the above most highly preferred metal coordination compoundsinclude compounds wherein the R' on the amido group is methyl, ethyl,propyl, butyl, pentyl, hexyl, (including isomers), norbomyl, benzyl,phenyl, etc.; the cyclopentadienyl group is cyclopentadienyl, indenyl,tetrahydroindenyl, fluorenyl, octahydrofluorenyl, etc.; R' on theforegoing cyclopentadienyl groups each occurrence is hydrogen, methyl,ethyl, propyl, butyl, pentyl hexyl (including isomers), norbornyl benzylphenyl etc.; and X is chloro, bromo, iodo, methyl, ethyl, propyl, butyl,pentyl, hexyl, (including isomers), norbornyl, benzyl, phenyl, etc.Specific compounds incude: (tert-butylamido)(tetramethyl-eta⁵-cyclopentadienyl)-1,2-ethanediylzirconium dichloride,(tert-butylamido)(tetramethyl-eta⁵-cyclopentadienyl)-1,2-ethanediyltitanium dichloride,(methylamido)(tetramethyl-eta⁵-cyclopentadienyl)-1,2-ethanediylzirconium dichloride,(methylamido)(tetramethyl-eta⁵ -cyclopentadienyl)-1,2-ethanediyltitaniumdichloride, (ethylamido)(tetramethyl-eta⁵-cyclopentadienyl)-methylenetitanium dichloro,(tertbutylamido)dibenzyl(tetramethyl-eta⁵ -cyclopentadienyl)silanezirconium dibenzyl, (benzylamido)dimethyl-(tetramethyl-eta⁵-cyclopentadienyl)silanetitanium dichloride,(phenylphosphido)dimethyl(tetramethyl-eta⁵-cyclopentadienyl)silanezirconium dibenzyl,(tertbutylamido)dimethyl(tetramethyl-eta⁵-cyclopentadienyl)silanetitanium dimethyl, and the like.

The complexes may be prepared by contacting a derivative of a metal, M,and a group I metal derivative or Grignard derivative of thecyclopentadienyl compound in a solvent and separating the salt byproductSuitable solvents for use in preparing the metal complexes are aliphaticor aromatic liquids such as cyclohexane, methylcyclohexane, pentane,hexane, heptane, tetrahydrofuran, diethyl ether, benzene, toluene,xylene, ethylbenzene, etc., or mixtures thereof.

In a preferred embodiment, the metal compound is MX_(n+1), i.e., M is ina lower oxidation state than in the corresponding compound, MX_(n+2) andthe oxidation state of M in the desired final complex. A noninterferingoxidizing agent may thereafter be employed to raise the oxidation stateof the metal. The oxidation is accomplished merely by contacting thereactants utilizing solvents and reaction conditions used in thepreparation of the complex itself. By the term "noninterfering oxidizingagent" is meant a compound having an oxidation potential sufficient toraise the metal oxidation state without interfering with the desiredcomplex formation or subsequent polymerization processes. A particularlysuitable noninterfering oxidizing agent is AgCl or an organic halidesuch as methylene chloride. The foregoing techniques are disclosed inU.S. Ser. No. 545,403, filed Jul. 3, 1990 and Ser. No. 702,475, filedMay 20, 1991, now abandoned the teachings of both of which areincorporated herein by reference.

Additionally the complexes may be prepared according to the teachings ofthe copending U.S. application Ser. No. 778,433 entitled: "Preparationof Metal Coordination Complex (I)", filed in the names of Peter Nickiasand David Wilson, on Oct. 15, 1991 now abandoned and the copending U.S.application Ser. No. 778,432 entitled: "Preparation of MetalCoordination Complex (II)", filed in the names of Peter Nickias andDavid Devore, on Oct. 15, 1991, now abandoned and the patents issuingtherefrom, all of which are incorporated herein by reference.

Suitable cocatalysts for use herein include polymeric or oligomericaluminoxanes, especially methyl aluminoxane, as well as inert,compatible, noncoordinating, ion forming compounds. So called modifiedmethyl aluminoxane (MMAO) is also suitable for use as a cocatalyst. Onetechnique for preparing such modified aluminoxane is disclosed in U.S.Pat. No. 5,041,584. Aluminoxanes can also be made as disclosed in U.S.Pat. Nos. 5,218,071; 5,086,024, 5,041,585, 5,041,583, 5,015,749,4,960,878 and 4,544,762 all of which are incorporated herein byreference. Aluminoxanes, including modified methyl aluminoxanes, whenused in the polymerization, are preferably used such that preferablyless than about 20 ppm aluminum, especially less than about 10 ppmaluminum, and more preferably less than about 5 ppm aluminum, fromcatalyst residue remain in the polymer. In order to measure the bulkpolymer properties (e.g. PI or melt fracture), aqueous HCl is used toextract the aluminoxane from the polymer. Preferred cocatalysts,however, are inert, noncoordinating, boron compounds such as thosedescribed in EP 520732 which is incorporated herein by reference.

Ionic active catalyst species which can be used to polymerize thepolymers described herein correspond to the formula: ##STR4## wherein: Mis a metal of group 3-10, or the Lanthanide series of the Periodic Tableof the Elements;

Cp* is a cyclopentadienyl or substituted cyclopentadienyl group bound inan eta⁵ bonding mode to M;

Z is a moiety comprising boron, or a member of group 14 of the PeriodicTable of the Elements, and optionally sulfur or oxygen, said moietyhaving up to 20 non-hydrogen atoms, and optionally Cp* and Z togetherform a fused ring system;

X independently each occurrence is an anionic ligand group or neutralLewis base ligand group having up to 30 non-hydrogen atoms;

n is 0, 1, 2, 3, or 4 and is 2 less than the valence of M; and

A- is a noncoordinating, compatible anion.

One method of making the ionic catalyst species which can be utilized tomake the polymers of the present invention involve combining:

a) at least one first component which is a mono(cyclopentadienyl)derivative of a metal of Group 3-10 or the Lanthanide Series of thePeriodic Table of the Elements containing at least one substituent whichwill combine with the cation of a second component (describedhereinafter) which first component is capable of forming a cationformally having a coordination number that is one less than its valence,and

b) at least one second component which is a salt of a Bronsted acid anda noncoordinating, compatible anion.

More particularly, the non-coordinating, compatible anion of theBronsted acid salt may comprise a single coordination complex comprisinga charge-bearing metal or metalloid core, which anion is both bulky andnon-nucleophilic. The recitation "metalloid", as used herein, includesnon-metals such as boron, phosphorus and the like which exhibitsemi-metallic characteristics.

Illustrative, but not limiting examples of monocyclopentadienyl metalcomponents (first components) which may be used in the preparation ofcationic complexes are derivatives of titanium, zirconium, vanadium,hafnium, chromium, lanthanum, etc. Preferred components are titanium orzirconium compounds. Examples of suitable monocyclopentadienyl metalcompounds are hydrocarbyl-substituted monocyclopentadienyl metalcompounds such as (tert-butylamido)(tetramethyl-eta⁵-cyclopentadienyl)-1,2-ethanediylzirconium dimethyl,(tert-butylamido)(tetramethyl-eta⁵-cyclopentadienyl)-1,2-ethanediyltitanium dimethyl,(methylamido)(tetramethyl-eta⁵-cyclopentadienyl)-1,2-ethanediylzirconium dibenzyl,(methylamido)(tetramethyl-eta⁵ -cyclopentadienyl)-1,2-ethanediyltitaniumdimethyl, (ethylamido)(tetramethyl-eta⁵-cyclopentadienyl)methylenetitanium dimethyl,(tertbutylamido)dibenzyl(tetramethyl-eta⁵-cyclopentadienyl)silanezirconium dibenzyl,(benzylamido)dimethyl(tetramethyl-eta⁵ -cyclopentadienyl)silanetitaniumdiphenyl, (phenylphosphido)dimethyl(tetramethyl-eta⁵-cyclopentadienyl)silanezirconium dibenzyl, and the like.

Such components are readily prepared by combining the correspondingmetal chloride with a dilithium salt of the substituted cyclopentadienylgroup such as a cyclopentadienyl-alkanediyl, cyclopentadienyl--silaneamide, or cyclopentadienyl--phosphide compound. The reaction isconducted in an inert liquid such as tetrahydrofuran, C₅₋₁₀ alkanes,toluene, etc. utilizing conventional synthetic procedures. Additionally,the first components may be prepared by reaction of a group IIderivative of the cyclopentadienyl compound in a solvent and separatingthe salt by-product. Magnesium derivatives of the cyclopentadienylcompounds are preferred. The reaction may be conducted in an inertsolvent such as cyclohexane, pentane, tetrahydrofuran, diethyl ether,benzene, toluene, or mixtures of the like. The resulting metalcyclopentadienyl halide complexes may be alkylated using a variety oftechniques. Generally, the metal cyclopentadienyl alkyl or arylcomplexes may be prepared by alkylation of the metal cyclopentadienylhalide complexes with alkyl or aryl derivatives of group I or group IImetals. Preferred alkylating agents are alkyl lithium and Grignardderivatives using conventional synthetic techniques. The reaction may beconducted in an inert solvent such as cyclohexane, pentane,tetrahydrofuran, diethyl ether, benzene, toluene, or mixtures of thelike. A preferred solvent is a mixture of toluene and tetrahydrofuran.

Compounds useful as a second component in the preparation of the ioniccatalysts useful in this invention will comprise a cation, which is aBronsted acid capable of donating a proton, and a compatiblenoncoordinating anion. Preferred anions are those containing a singlecoordination complex comprising a charge-bearing metal or metalloid corewhich anion is relatively large (bulky), capable of stabilizing theactive catalyst species (the Group 3-10 or Lanthanide Series cation)which is formed when the two components are combined and sufficientlylabile to be displaced by olefinic, diolefinic and acetylenicallyunsaturated substrates or other neutral Lewis bases such as ethers,nitriles and the like. Suitable metals, then, include, but are notlimited to, aluminum, gold, platinum and the like. Suitable metalloidsinclude, but are not limited to, boron, phosphorus, silicon and thelike. Compounds containing anions which comprise coordination complexescontaining a single metal or metalloid atom are, of course, well knownand many, particularly such compounds containing a single boron atom inthe anion portion, are available commercially. In light of this, saltscontaining anions comprising a coordination complex containing a singleboron atom are preferred.

Highly preferably, the second component useful in the preparation of thecatalysts of this invention may be represented by the following generalformula:

    (L--H)+ A!-

wherein:

L is a neutral Lewis base;

(L--H)+ is a Bronsted acid; and

A!- is a compatible, noncoordinating anion.

More preferably A!- corresponds to the formula:

     M'Q.sub.q !-

wherein:

M' is a metal or metalloid selected from Groups 5-15 of the PeriodicTable of the Elements; and

Q independently each occurrence is selected from the Group consisting ofhydride, dialkylamido, halide, alkoxide, aryloxide, hydrocarbyl, andsubstituted-hydrocarbyl radicals of up to 20 carbons with the provisothat in not more than one occurrence is Q halide and q is one more thanthe valence of M'.

Second components comprising boron which are particularly useful in thepreparation of catalysts of this invention may be represented by thefollowing general formula:

     L--H!+ BQ.sub.4 !-

wherein:

L is a neutral Lewis base;

L--H!+ is a Bronsted acid;

B is boron in a valence state of 3; and

Q is as previously defined.

Illustrative, but not limiting, examples of boron compounds which may beused as a second component in the preparation of the improved catalystsof this invention are trialkyl-substituted ammonium salts such astriethylammonium tetraphenylborate, tripropylammonium tetraphenylborate,tris(n-butyl)ammonium tetraphenylborate, trimethylammoniumtetrakis(p-tolyl)borate, tributylammoniumtetrakis(pentafluorophenyl)borate, tripropylammoniumtetrakis(2,4-dimethylphenyl)borate, tributylammoniumtetrakis(3,5-dimethylphenyl)borate, triethylammoniumtetrakis(3,5-di-trifluoromethylphenyl)borate and the like. Also suitableare N,N-dialkyl anilinium salts such asN,N-methyl-aniliniumtetraphenylborate, N,N-diethylaniliniumtetraphenylborate, N,N-2,4,6-pentamethylanilinium tetraphenylborate andthe like; dialkylammonium salts such as di-(i-propyl)ammoniumtetrakis(pentafluorophenyl)borate, dicyclohexylammoniumtetraphenylborate and the like; and triaryl phosphonium salts such astriphenylphosphonium tetraphenylborate, tri(methylphenyl)tetrakiniumtetrakis-pentafluorophenylborate, tri(dimethylphenyl)phosphoniumtetraphenylborate and the like.

Preferred ionic catalysts are those having a limiting charge separatedstructure corresponding to the formula: ##STR5## wherein: M is a metalof group 3-10, or the Lanthanide series of the Periodic Table of theElements;

Cp* is a cyclopentadienyl or substituted cyclopentadienyl group bound inan eta⁵ bonding mode to M;

Z is a moiety comprising boron, or a member of group 14 of the PeriodicTable of the Elements, and optionally sulfur or oxygen, said moietyhaving up to 20 non-hydrogen atoms, and optionally Cp* and Z togetherform a fused ring system;

X independently each occurrence is an anionic ligand group or neutralLewis base ligand group having up to 30 non-hydrogen atoms;

n is 0, 1, 2, 3, or 4 and is 2 less than the valence of M; and

XA*-- is --XB(C₆ F₅)₃.

This class of cationic complexes may be conveniently prepared bycontacting a metal compound corresponding to the formula: ##STR6##wherein: Cp*, M, and n are as previously defined, withtris(pentafluorophenyl)borane cocatalyst under conditions to causeabstraction of X and formation of the anion --XB(C₆ F₅)₃.

Preferably X in the foregoing ionic catalyst is C₁ -C₁₀ hydrocarbyl,most preferably methyl.

The preceding formula is referred to as the limiting, charge separatedstructure. However, it is to be understood that, particularly in solidform, the catalyst may not be fully charge separated. That is, the Xgroup may retain a partial covalent bond to the metal atom, M. Thus, thecatalysts may be alternately depicted as possessing the formula:##STR7##

The catalysts are preferably prepared by contacting the derivative of aGroup 4 or Lanthanide metal with the tris(pentafluorophenyl)borane in aninert diluent such as an organic liquid.

Tris(pentafluorphenyl)borane is a commonly available Lewis acid that maybe readily prepared according to known techniques. The compound isdisclosed in Marks, et al. J. Am. Chem. Soc. 1991, 113, 3623-3625 foruse in alkyl abstraction of zirconocenes.

All reference to the Periodic Table of the Elements herein shall referto the Periodic Table of the Elements, published and copyrighted by CRCPress, Inc., 1989. Also, any reference to a Group or Groups shall be tothe Group or Groups as reflected in this Periodic Table of the Elementsusing the IUPAC system for numbering groups.

It is believed that in the constrained geometry catalysts used hereinthe metal atom is forced to greater exposure of the active metal sitebecause one or more substituents on the single cyclopentadienyl orsubstituted metal is both bonded to an adjacent covalent moiety and heldin association with the cyclopentadienyl group through an eta⁵ or otherpi-bonding interaction. It is understood that each respective bondbetween the metal atom and the constituent atoms of the cyclopentadienylor substituted cyclopentadienyl group need not be equivalent. That is,the metal may be symmetrically or unsymmetrically pi-bound to thecyclopentadienyl or substituted cyclopentadienyl group.

The geometry of the active metal site is further defined as follows. Thecentroid of the cyclopentadienyl or substituted cyclopentadienyl groupmay be defined as the average of the respective X, Y, and Z coordinatesof the atomic centers forming the cyclopentadienyl or substitutedcyclopentadienyl group. The angle, theta, formed at the metal centerbetween the centroid of the cyclopentadienyl or substitutedcyclopentadienyl group and each other ligand of the metal complex may beeasily calculated by standard techniques of single crystal X-raydiffraction Each of these angles may increase or decrease depending onthe molecular structure of the constrained geometry metal complex. Thosecomplexes wherein one or more of the angles, theta, is less than in asimilar, comparative complex differing only in the fact that theconstrain inducing substituent is replaced by hydrogen, have constrainedgeometry for purposes of the present invention. Preferably one or moreof the above angles, theta, decrease by at least 5 percent, morepreferably 7.5 percent, compared to the comparative complex. Highlypreferably, the average value of all bond angles, theta, is also lessthan in the comparative complex.

Preferably, monocyclopentadienyl metal coordination complexes of group 4or lanthanide metals according to the present invention have constrainedgeometry such that the smallest angle, theta, between the centroid ofthe Cp* group and the Y substituent, is less than 115 degrees, morepreferably less than 110 degrees, most preferably less than 105 degrees,and especially less than 100 degrees.

Other compounds which are useful in the catalyst compositions of thisinvention, especially compounds containing other Group 4 or Lanthanidemetals, will, of course, be apparent to those skilled in the art.

Polymerization

The improved melt elasticity and processibility of the substantiallylinear polymers according to the present invention result, it isbelieved, from their method of production. The polymers may be producedvia a continuous (as opposed to a batch) controlled polymerizationprocess using at least one reactor (e.g., as disclosed in WO 93/07187,WO 93/07188, and WO 93/07189, the disclosures of each of which isincorporated herein by reference), but can also be produced usingmultiple reactors (e.g., using a multiple reactor configuration asdescribed in U.S. Pat. No. 3,914,342, the disclosure of which isincorporated herein by reference) at a polymerization temperature andpressure sufficient to produce the interpolymers having the desiredproperties.

While not wishing to be bound by any particular theory, the inventorsbelieve that long chain branches are formed in their novel polymersaccording to the following sequence:

Propagation Step

R--(C₂ H₄)+Catalyst→R--C₂ H₄ -Catalyst

Termination Step

R--C₂ H₄ -Catalyst→R--CH═CH₂ (beta-hydride elimination)

Copolymerization

R--CH₂ --CH₂ --CHR'--CH₂ -Catalyst→R--CH₂ --CH₂ --CHR'--CH₂ -Catalyst

Continued Polymerization

R--CH₂ --CH₂ --CHR'--CH₂ -Catalyst+(C₂ H₄)_(x) →R--CHR'(CH₂ CH₂)_(x)-Catalyst

Termination Step

1) R--CHR'(CH₂ CH₂)_(x) -Catalyst+Heat→R--CHR'R"CH═CH₂ +H-Catalyst

2) R--CHR'(CH₂ CH₂)_(x) -Catalyst+H₂ →R--CHR'R"+H-Catalyst

wherein:

R=growing polymer chain

R'=long chain branch (LCB), and

R"=growing polymer chain after insertion of R".

In polymerizing ethylene and ethylene/alpha-olefin copolymers, a batchreactor process typically operates at an ethylene concentration fromabout 6.7 to about 12.5 percent by weight of the reactor contents andhave a polymer concentration generally less than about 5 percent byweight of the reactor contents, dependent upon the ethylene solubility,which is a function of reactor diluent, temperature and pressure. Theinitial polymer concentration is zero and increases over time as thereaction proceeds such that the highest polymer concentration occurs atthe end of the reaction, the point at which the catalyst is spent. Mostof the polymer is made during the initial minutes of the polymerization.

According to one embodiment of the present process, the polymers areproduced in a continuous process operated at a steady state (i.e. thereactants are fed to the reactor at a rate in substantially in balancewith the rate that product is removed from the reactor such that thereaction mass in the reactor is relatively constant in volume andcomposition), as opposed to a batch process. Preferably, thepolymerization temperature of the continuous process is from about 20 C.to about 250 C., using constrained geometry catalyst technology. If anarrow molecular weight distribution polymer (M_(w) /M_(n) of from about1.5 to about 2.5) having a higher I₁₀ /I₂ ratio (e.g. I₁₀ /I₂ of 7 ormore, preferably at least 8, especially at least 9 and as high as about20 or more) is desired, the ethylene concentration in the reactor ispreferably not more than about 8 percent by weight of the reactorcontents, especially not more than about 6 percent by weight of thereactor contents, and most especially not more than about 4 percent byweight of the reactor contents, and as low as about 0.75 percent byweight of the reactor contents.

Preferably, the polymerization is performed in a solution polymerizationprocess. Generally, manipulation of I₁₀ /I₂ while holding M_(w) /M_(n)relatively low for producing the novel polymers described herein is afunction of reactor temperature and/or ethylene concentration.

Surprisingly, reduced ethylene concentration and higher temperaturegenerally produces higher I₁₀ /I₂. Generally, as the percent of ethyleneis converted into polymer, the ethylene concentration in the reactordecreases and the polymer concentration increases. For the novelsubstantially linear ethylene-alpha-olefin copolymers and substantiallylinear ethylene homopolymers claimed herein, the polymer concentrationfor a continuous solution polymerization process is preferably aboveabout 5 weight percent of the reactor contents, especially above about15 weight percent of the reactor contents, and as high as about 40weight percent of the reactor contents. Typically greater than 70percent, preferably greater than 80 percent and more preferably greaterthan 90 percent, of the ethylene is converted to polymer.

The substantially linear polymers of the present invention can beethylene homopolymers, or they can be interpolymers of ethylene with atleast one C₃ -C₂₀ alpha-olefin and/or C₄ -C₁₈ diolefins. Thesubstantially linear polymers of the present invention can also beinterpolymers of ethylene with at least one of the above C₃ -C₂₀alpha-olefins and/or diolefins in combination with other unsaturatedmonomers.

Monomers usefully copolymerized or interpolymerized with ethyleneaccording to the present invention include, for example, ethylenicallyunsaturated monomers, conjugated or nonconjugated dienes, polyenes, etc.Preferred comonomers include the C₃ -C₁₀ alpha-olefins especiallypropene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and1-octene. Other preferred monomers include styrene, halo- or alkylsubstituted styrenes, vinylbenzocyclobutene, 1,4-hexadiene, andnaphthenics (e.g., cyclo-pentene, cyclo-hexene and cyclo-octene).

Other unsaturated monomers usefully copolymerized according to thepresent invention include, for example, ethylenically unsaturatedmonomers, conjugated or nonconjugated dienes, polyenes, etc. Preferredcomonomers include the C₃ -C₁₀ alpha-olefins especially propene,isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Otherpreferred comonomers include styrene, halo- or alkyl substitutedstyrenes, vinylbenzocyclobutene, 1,4-hexadiene, and naphthenics (e.g.,cyclopentene, cyclohexene and cyclooctene).

The polymerization conditions for manufacturing the polymers of thepresent invention are generally those useful in the solutionpolymerization process, although the application of the presentinvention is not limited thereto. Slurry and gas phase polymerizationprocesses are also believed to be useful, provided the proper catalystsand polymerization conditions are employed.

Multiple reactor polymerization processes are also useful in the presentinvention, such as those disclosed in U.S. Pat. No. 3,914,342. Themultiple reactors can be operated in series or in parallel, with atleast one constrained geometry catalyst employed in at least one of thereactors.

In general, the continuous polymerization according to the presentinvention may be accomplished at conditions well known in the prior artfor Ziegler-Natta or Kaminsky-Sinn type polymerization reactions, thatis, temperatures from 0 to 250 C. and pressures from atmospheric to 1000atmospheres (100 MPa). Suspension, solution, slurry, gas phase or otherprocess conditions may be employed if desired. A support may beemployed, but preferably the catalysts are used in a homogeneous (i.e.,soluble) manner. It will, of course, be appreciated that the activecatalyst system form in situ if the catalyst and the cocatalystcomponents thereof are added directly to the polymerization process anda suitable solvent or diluent, including condensed monomer, is used insaid polymerization process. It is, however, preferred to form theactive catalyst in a separate step in a suitable solvent prior to addingthe same to the polymerization mixture.

The polymerization conditions for manufacturing the polymers of thepresent invention are generally those useful in the solutionpolymerization process, although the application of the presentinvention is not limited thereto. Gas phase polymerization processes arealso believed to be useful, provided the proper catalysts andpolymerization conditions are employed.

Fabricated articles made from the novel ethylene polymers may beprepared using all of the conventional polyethylene processingtechniques. Useful articles include films (e.g., cast, blown andextrusion coated), fibers (e.g., staple fibers (including use of a novelethylene polymer disclosed herein as at least one component comprisingat least a portion of the fiber's surface), spunbond fibers or meltblown fibers (using, e.g., systems as disclosed in U.S. Pat. No.4,340,563, U.S. Pat. No. 4,663,220, U.S. Pat. No. 4,668,566, or U.S.Pat. No. 4,322,027), and gel spun fibers (e.g., the system disclosed inU.S. Pat. No. 4,413,110)), both woven and nonwoven fabrics (e.g.,spunlaced fabrics disclosed in U.S. Pat. No. 3,485,706) or structuresmade from such fibers (including, e.g., blends of these fibers withother fibers, e.g., PET or cotton) and molded articles (e.g., made usingan injection molding process, a blow molding process or a rotomoldingprocess). The new polymers described herein are also useful for wire andcable coating operations, impact modification, especially at lowtemperatures, of thermoplastic olefins (e.g., polypropylene), as well asin sheet extrusion for vacuum forming operations, closed cell and opencell foams (including radiation and chemically crosslinked foams andfoam structures), and adhesives. All of the preceding patents areincorporated herein by reference.

Useful compositions are also suitably prepared comprising thesubstantially linear polymers of the present invention and at least oneother natural or synthetic polymer. Preferred other polymers includethermoplastics such as styrene-butadiene block copolymers, polystyrene(including high impact polystyrene), ethylene vinyl acetate copolymers,ethylene acrylic acid copolymers, other olefin copolymers (especiallypolyethylene copolymers) and homopolymers (e.g., those polyethylenecopolymers and homopolymers made using conventional heterogeneouscatalysts). Examples of such heterogeneous polyethylene polymers andcopolymers include polymers made by the process of U.S. Pat. No.4,076,698 (incorporated herein by reference), other linear orsubstantially linear polymers of the present invention, and mixturesthereof. Other substantially linear polymers of the present inventionand conventional heterogeneously branched HDPE and/or heterogeneouslybranched LLDPE are preferred for use in the thermoplastic compositions.

The compositions comprising the substantially linear ethylene polymersare formed by any convenient method, including dry blending theindividual components and subsequently melt mixing, either directly inthe extruder used to make the finished article (e.g., film), or bypre-melt mixing in a separate extruder. The polyethylene compositionsmay also be prepared by multiple reactor polymerization techniques. Forexample, one reactor may polymerize the constrained geometry catalyzedpolyethylene and another reactor polymerize the heterogeneous catalyzedpolyethylene, either in series or in parallel operation.

Compositions comprising the ethylene polymers can also be formed intofabricated articles such as those previously mentioned usingconventional polyethylene processing techniques which are well known tothose skilled in the art of polyethylene processing.

For examples described herein, unless otherwise stipulated, allprocedures were performed under an inert atmosphere of nitrogen orargon. Solvent choices were often optional, for example, in most caseseither pentane or 30-60 petroleum ether can be interchanged. Amines,silanes, lithium reagents, and Grignard reagents were purchased fromAldrich Chemical Company. Published methods for preparingtetramethylcyclopentadiene (C₅ Me₄ H₂) and lithiumtetramethylcyclopentadienide (Li(C₅ Me₄ H)) include C. M. Fendrick etal. Organometallics, 3, 819 (1984). Lithiated substitutedcyclopentadienyl compounds may be typically prepared from thecorresponding cyclopentadiene and a lithium reagent such as n-butyllithium. Titanium trichloride (TiCl₃) was purchased from AldrichChemical Company. The tetrahydrofuran adduct of titanium trichloride,TiCl₃ (THF)₃, was prepared by refluxing TiCl₃ in THF overnight, cooling,and isolating the blue solid product, according to the procedure of L.E. Manzer, Inorg. Syn., 21, 135 (1982).

EXAMPLES 1-4

The metal complex solution for Example 1 is prepared as follows:

Part 1: Prep of Li(C₅ Me₄ H)

In the drybox, a 3 L 3-necked flask was charged with 18.34 g of C₅ Me₄H₂, 800 mL of pentane, and 500 mL of ether. The flask was topped with areflux condenser, a mechanical stirrer, and a constant addition funnelcontainer 63 mL of 2.5M n-BuLi in hexane. The BuLi was added dropwiseover several hours. A very thick precipitate formed; approx. 1000 mL ofadditional pentane had to be added over the course of the reaction toallow stirring to continue. After the addition was complete, the mixturewas stirred overnight. The next day, the material was filtered, and thesolid was thoroughly washed with pentane and then dried under reducedpressure. 14.89 g of Li(C₅ Me₄ H) was obtained (78 percent).

Part 2: Prep of C₅ Me₄ HSiMe₂ Cl

In the drybox 30.0 g of Li(C₅ Me₄ H) was placed in a 500 mL Schlenkflask with 250 mL of THF and a large magnetic stir bar. A syringe wascharged with 30 mL of Me₂ SiCl₂ and the flask and syringe were removedfrom the drybox. On the Schlenk line under a flow of argon, the flaskwas cooled to -78 C., and the Me₂ SiCl₂ added in one rapid addition. Thereaction was allowed to slowly warm to room temperature and stirredovernight. The next morning the volatile materials were removed underreduced pressure, and the flask was taken into the drybox. The oilymaterial was extracted with pentane, filtered, and the pentane wasremoved under reduced pressure to leave the C₅ Me₄ HSiMe₂ Cl as a clearyellow liquid (46.83 g; 92.9 percent).

Part 3: Prep of C₅ Me₄ HSiMe₂ NH^(t) Bu

In the drybox, a 3-necked 2 L flask was charged with 37.4 g oft-butylamine and 210 mL of THF. C₅ Me₄ HSiMe₂ Cl (25.47 g) was slowlydripped into the solution over 3-4 hours. The solution turned cloudy andyellow. The mixture was stirred overnight and the volatile materialsremoved under reduced pressure. The residue was extracted with diethylether, the solution was filtered, and the ether removed under reducedpressure to leave the C₅ Me₄ HSiMe₂ NH^(t) Bu as a clear yellow liquid(26.96 g; 90.8 percent).

Part 4: Prep of MgCl!₂ Me₄ C₅ SiMe₂ N^(t) Bu!(THF)_(x)

In the drybox, 14.0 mL of 2.0M isopropylmagnesium chloride in ether wassyringed into a 250 mL flask. The ether was removed under reducedpressure to leave a colorless oil. 50 mL of a 4:1 (by volume)toluene:THF mixture was added followed by 3.50 g of Me₄ HC₅ SiMe₂ NH^(t)Bu. The solution was heated to reflux. After refluxing for 2 days, thesolution was cooled and the volatile materials removed under reducedpressure. The white solid residue was slurried in pentane and filteredto leave a white powder, which was washed with pentane and dried underreduced pressure. The white powder was identified as MgCl!₂ Me₄ C₅ SiMe₂N^(t) Bu!(THF)_(x) (yield:6.7 g).

Part 5: Prep of C₅ Me₄ (SiMe₂ N^(t) Bu)!TiCl₂

In the drybox, 0.50 g of TiCl₃ (THF)₃ was suspended in 10 mL of THF.0.69 g of solid MgCl!₂ Me₄ C₅ SiMe₂ N^(t) Bu!(THF)_(x) was added,resulting in a color change from pale blue to deep purple. After 15minutes, 0.35 g of AgCl was added to the solution. The color immediatelybegan to lighten to a pale green/yellow. After 1.5 hours, the THF wasremoved under reduced pressure to leave a yellow-green solid. Toluene(20 mL) was added, the solution was filtered, and the toluene wasremoved under reduced pressure to leave a yellow-green solid, 0.51 g(quantitative yield) identified by 1H NMR as C₅ Me₄ (SiMe₂ N^(t)Bu)!TiCl₂.

Part 6: Preparation of C₅ Me₄ (SiMe₂ N^(t) Bu)!TiMe₂

In an inert atmosphere glove box, 9.031 g of C₅ Me₄ (Me₂ SiN^(t)Bu)!TiCl₂ is charged into a 250 ml flask and dissolved into 100 ml ofTHF. This solution is cooled to about -25 C. by placement in the glovebox freezer for 15 minutes. To the cooled solution is added 35 ml of a1.4M MeMgBr solution in toluene/THF (75/25). The reaction mixture isstirred for 20 to 25 minutes followed by removal of the solvent undervacuum. The resulting solid is dried under vacuum for several hours. Theproduct is extracted with pentane (4×50 ml) and filtered. The filtrateis combined and the pentane removed under vacuum giving the catalyst asa straw yellow solid.

The metal complex, C₅ Me₄ (SiMe₂ N^(t) Bu)!TiMe₂, solution for Examples2 and 3 is prepared as follows:

In an inert atmosphere glove box 10.6769 g of a tetrahydrofuran adductof titanium trichloride, TiCl₃ (THF)₃, is loaded into a 1 L flask andslurried into 300 ml of THF. To this slurry, at room temperature, isadded 17.402 g of MgCl!₂ N^(t) BuSiMe₂ C₅ Me₄ !(THF)_(x) as a solid. Anadditional 200 ml of THF is used to help wash this solid into thereaction flask. This addition resulted in an immediate reaction giving adeep purple solution. After stirring for 5 minutes 9.23 ml of a 1.56Msolution of CH₂ Cl₂ in THF is added giving a quick color change to darkyellow. This stage of the reaction is allowed to stir for about 20 to 30minutes. Next, 61.8 ml of a 1.4M MeMgBr solution in toluene/THF(75/25)is added via syringe. After about 20 to 30 minutes stirring time thesolvent is removed under vacuum and the solid dried. The product isextracted with pentane (8×50 ml) and filtered. The filtrate is combinedand the pentane removed under vacuum giving the metal complex as a tansolid.

The metal complex, C₅ Me₄ (SiMe₂ N^(t) Bu)!TiMe₂, solution for Example 4is prepared as follows:

In an inert atmosphere glove box 4.8108 g of TiCl₃ (THF)₃ is placed in a500 ml flask and slurried into 130 ml of THF. In a separate flask 8.000g of MgCl!₂ N^(t) BuSiMe₂ C₅ Me₄ !(THF)_(x) is dissolved into 150 ml ofTHF. These flasks are removed from the glove box and attached to avacuum line and the contents cooled to -30 C. The THF solution of MgCl!₂N^(t) BuSiMe₂ C₅ Me₄ !(THF)_(x) is transferred (over a 15 minute period)via cannula to the flask containing the TiCl₃ (THF)₃ slurry. Thisreaction is allowed to stir for 1.5 hours over which time thetemperature warmed to 0 C. and the solution color turned deep purple.The reaction mixture is cooled back to -30 C. and 4.16 ml of a 1.56M CH₂Cl₂ solution in THF is added. This stage of the reaction is stirred foran additional 1.5 hours and the temperature warmed to -10 C. Next, thereaction mixture is again cooled to -40 C. and 27.81 ml of a 1.4M MeMgBrsolution in toluene/THF (75/25) was added via syringe and the reactionis now allowed to warm slowly to room temperature over 3 hours. Afterthis time the solvent is removed under vacuum and the solid dried. Atthis point the reaction flask is brought back into the glove box wherethe product is extracted with pentane (4×50 ml) and filtered. Thefiltrate is combined and the pentane removed under vacuum giving thecatalyst as a tan solid. The metal complex is then dissolved into amixture of C₈ -C₁₀ saturated hydrocarbons (e.g., Isopar™ E, made byExxon) and ready for use in polymerization.

Polymerization

The polymer products of Examples 1-4 are produced in a solutionpolymerization process using a continuously stirred reactor. Additives(e.g., antioxidants, pigments, etc.) can be incorporated into theinterpolymer products either during the pelletization step or aftermanufacture with a subsequent re-extrusion. Examples 1-4 are eachstabilized with 1250 ppm calcium stearate, 200 ppm Irganox 1010, and1600 ppm Irgafos 168. Irgafos™ 168 is a phosphite stabilizer andIrganox™ 1010 is a hindered polyphenol stabilizer (e.g., tetrakismethylene 3-(3,5-ditertbutyl-4-hydroxyphenylpropionate)!methane. Bothare trademarks of and made by Ciba-Geigy Corporation. A representativeschematic for the polymerization process is shown in FIG. 1.

The ethylene (4) and the hydrogen are combined into one stream (15)before being introduced into the diluent mixture (3). Typically, thediluent mixture comprises a mixture of C₈ -C₁₀ saturated hydrocarbons(1), (e.g., Isopar™E, made by Exxon) and the comonomer(s) (2). ForExample 1, the comonomer is 1-octene. The reactor feed mixture (6) iscontinuously injected into the reactor (9). The metal complex (7) andthe cocatalyst (8) (the cocatalyst is tris(pentafluorophenyl)borane forExamples 1-4 herein which forms the ionic catalyst in situ) are combinedinto a single stream and also continuously injected into the reactor.Sufficient residence time is allowed for the metal complex andcocatalyst to react to the desired extent for use in the polymerizationreactions, at least about 10 seconds. For the polymerization reactionsof Examples 1-4, the reactor pressure is held constant at about 490psig. Ethylene content of the reactor, after reaching steady state, ismaintained below about 8 percent.

After polymerization, the reactor exit stream (14) is introduced into aseparator (10) where the molten polymer is separated from the unreactedcomonomer(s), unreacted ethylene, unreacted hydrogen, and diluentmixture stream (13). The molten polymer is subsequently strand choppedor pelletized and, after being cooled in a water bath or pelletizer(11), the solid pellets are collected (12). Table 1 describes thepolymerization conditions and the resultant polymer properties:

                  TABLE I                                                         ______________________________________                                        Example          1*      2       3     4                                      ______________________________________                                        Ethylene feed rate (lbs/hour)                                                                  3.2     3.8     3.8   3.8                                    Comonomer/Total Olefin ratio*                                                                  12.3    0       0     0                                      (mole percent)                                                                Hydrogen/ethylene ratio                                                                        0.054   0.072   0.083 0.019                                  (mole percent)                                                                Diluent/ethylene ratio                                                                         9.5     7.4     8.7   8.7                                    (weight basis)                                                                Metal complex conc.                                                                            0.00025 0.0005  0.001 0.001                                  (molar)                                                                       Metal complex flow rate (ml/min)                                                               5.9     1.7     2.4   4.8                                    Cocatalyst conc. 0.001   0.001   0.002 0.002                                  (molar)                                                                       Cocatalyst flow rate (ml/min)                                                                  2.9     1.3     6     11.9                                   Reactor temp (EC)                                                                              114     160     160   200                                    Polymer concentration (wt %) in                                                                7.1     8.4     9.5   8.4                                    the reactor exit stream                                                       Comonomer concentration (wt %)                                                                 3.8     0       0     0                                      in the reactor exit stream                                                    Ethylene conc. in the reactor exit                                                             2.65    3.59    0.86  1.98                                   stream (weight percent)                                                       Product I.sub.2  1.22    0.96    1.18  0.25                                   (g/10 minutes)                                                                Product density  0.903   0.954   0.954 0.953                                  (g/cm.sup.3)                                                                  Product I.sub.10 /I.sub.2                                                                      6.5     7.4     11.8  16.1                                   Single DSC Melting Peak (C)                                                                    97      132     131   132                                    Product M.sub.w  95,400  93,800  71,600                                                                              105,800                                Product M.sub.n  50,000  48,200  34,200                                                                              51,100                                 Product M.sub.w /M.sub.n                                                                       1.91    1.95    2.09  2.07                                   Ethylene Conversion (%)                                                                        71      70      92    81                                     LCB/Chain        N.M.**  --      0.53  0.66                                   LCB/10,000 Carbons                                                                             N.M.**  --      2.2   1.8                                    Aluminium Residue (ppm)                                                                        0       0       0     0                                      ______________________________________                                         *For Example 1, the Comonomer/Total Olefin ratio is defined as the            percentage molar ratio of 1octene/(1-octene + ethylene). Ex. 1* is a          Comparative Example since the copolymer has onset of gross melt fracture      less than 4 × 10.sup.6 dyne/cm.sup.2.                                   **N.M. = Not Measured.                                                   

The ¹³ C NMR spectrum of Example 3 (ethylene homopolymer) shows peakswhich can be assigned to the alpha,delta⁺, beta,delta⁺ and methinecarbons associated with a long chain branch. Long chain branching isdetermined using the method of Randall described earlier in thisdisclosure, wherein he states that "Detection of these resonances inhigh-density polyethylenes where no 1-olefins were added during thepolymerization should be strongly indicative of the presence of longchain branching." Using the equation 141 from Randall (p. 292):

    Branches per 10,000 carbons= 1/3(alpha)/T.sub.Tot !×10.sup.4,

wherein alpha=the average intensity of a carbon from a branch(alpha,delta+) carbon and T_(Tot) =the total carbon intensity. Thenumber of long chain branches in this sample is determined to be 3.4 per10,000 total carbon atoms, or 0.34 long chain branches/1000 total carbonatoms using 300 MHz ¹³ C NMR, and 2.2 per 10,000 total carbon atoms, or0.22 long chain branches/1000 total carbon atoms using a 600 MHz ¹³ CNMR.

EXAMPLES 5, 6 AND COMPARATIVE EXAMPLES 7-9

Examples 5, 6 and Comparison Examples 7-9 with the same melt index aretested for rheology Comparison. Examples 5 and 6 are the substantiallylinear ethylene/1-octene copolymers produced by the constrained geometrycatalyst technology, as described in Example 1, with the exception thatlower ethylene concentrations were used for Examples 5 and 6 providingfor higher I₁₀ /I₂ ratios and consequently more long chain branchingthan Example 1. Examples 5 and 6 are stabilized as Examples 1-4.Comparison Examples 7, 8 and 9 are conventional heterogeneous Zieglerpolymerization blown film resins Dowlex™ 2045A, Attane™ 4201, andAttane™ 4403, respectively, all of which are ethylene/1-octenecopolymers made by The Dow Chemical Company.

Comparative Example 7 is stablized with 200 ppm Irganox™ 1010, and 1600ppm Irgafos™ 168 while Comparative Examples 8 and 9 are stablized with200 ppm Irganox™ 1010 and 800 ppm PEPQ™. PEPQ™ is a trademark of SandozChemical, the primary ingredient of which is believed to betetraki-(2,4-di-tertbutyl-phenyl)4,4'biphenylphosphonite. A comparisonof the physical properties of each Example and Comparative Example islisted in Table II.

                  TABLE II                                                        ______________________________________                                                                  Compara-                                                                             Compara-                                                                             Compara-                                                        tive   tive   tive                                  Property  Ex. 5   Ex. 6   Example 7                                                                            Example 8                                                                            Example 9                             ______________________________________                                        I.sub.2   1       1       1      1      0.76                                  (g/10 minutes)                                                                Density   0.92    0.902   0.92   0.912  0.905                                 (g/cm.sup.3)                                                                  I.sub.10 /I.sub.2                                                                       945     7.61    7.8-8  8.2    8.7                                   product M.sub.w                                                                         73,800  96,900  124,600                                                                              122,500                                                                              135,300                               Product M.sub.n                                                                         37,400  46,400  34,300 32,500 31,900                                Product M.sub.w /M.sub.n                                                                1.97    2.09    3.5-3.8                                                                              3.8    3.8-4.2                               DSC Melt Peak(s)                                                                        111     95      114, 118,                                                                            100, 116,                                                                            96, 116,                              (C)                       122    121    121                                   ______________________________________                                    

Surprisingly, even though the molecular weight distribution of Examples5 and 6 is narrow (i.e., M_(w) /M_(n) is low), the I₁₀ /I₂ values arecomparable or higher in comparison with Comparative Examples 7-9. Acomparison of the relationship between I₁₀ /I₂ vs. M_(w) /M_(n) for someof the novel polymers described herein and conventional heterogeneousZiegler polymers is given in FIG. 2. The I₁₀ /I₂ value for the novelpolymers of the present invention is essentially independent of themolecular weight distribution, M_(w) /M_(n) which is not true forconventional Ziegler polymerized resins.

Example 5 and Comparative Example 7 with similar melt index and density(Table II) are also extruded via a Gas Extrusion Rheometer (GER) at 190C. using a 0.0296" diameter, 20:1 L/D die. The processing index (P.I.)is measured at an apparent shear stress of 2.15×10⁶ dyne/cm² asdescribed previously. The onset of gross melt fracture can easily beidentified from the shear stress vs. shear rate plot shown in FIG. 3where a sudden jump of shear rate occurs. A comparison of the shearstresses and corresponding shear rates before the onset of gross meltfracture is listed in Table III. It is particularly interesting that thePI of Example 5 is more than 20 percent lower than the PI of ComparativeExample 7 and that the onset of melt fracture or sharkskin for Example 5is also at a significantly higher shear stress and shear rate incomparison with the Comparative Example 7. Furthermore, the Melt Tension(MT) as well as Elastic Modulus of Example 5 are higher than that ofComparative Example 7.

Note that each of the Comparative Examples 7-9 has three distinctmelting peaks as measured by DSC, which is evidence of theirheterogeneous branching distribution. In contrast, the polymers ofExamples 5 and 6 have a single melting peak as measured by DSC betweenthe temperatures of -30 and 150 C. which is evidence of the homogeneityof the polymers branching distribution. Furthermore, the single meltingpeaks of Examples 5 and 6 indicate that each polymer is not a "blend"unlike the polymers disclosed in U.S. Pat. No. 5,218,071.

                  TABLE III                                                       ______________________________________                                                                     Comparative                                      Property          Example 5  Example 7                                        ______________________________________                                        I.sub.2           1          1                                                (g/10 minutes)                                                                I.sub.10 /I.sub.2 9.45       7.8-8                                            PI (kpoise)       11         15                                               Melt tension (gms)                                                                              1.89       1.21                                             Elastic modulus at 0.1                                                                          2425       882.6                                            rad/sec                                                                       (dynes/cm.sup.2)                                                              OGMF*, critical shear rate                                                                      >1556      936                                              (l/sec)           (not observed)                                              OGMF*, critical shear stress                                                                    ≧0.452                                                                            0.366                                            (MPa)             (not observed)                                              OSMF**, critical shear rate                                                                     >1566      about 628                                        (l/sec)           (not observed)                                              OSMF**, critical shear stress                                                                   ≧0.452                                                                            about 0.25                                       (MPa)             (not observed)                                              ______________________________________                                         *Onset of Gross Melt Fracture.                                                **Onset of Surface Melt Fracture.                                        

Example 6 and Comparison Example 9 have similar melt index and density,but Example 6 has lower I₁₀ /I₂ (Table IV). These polymers are extrudedvia a Gas Extrusion Rheometer (GER) at 190 C. using a 0.0296 inchdiameter, 20:1 L/D die. The processing index (PI) is measured at anapparent shear stress of 2.15×10⁶ dyne/cm² as described previously.

                  TABLE IV                                                        ______________________________________                                                                   Comparative                                        Property          Example 6                                                                              Example 9                                          ______________________________________                                        I.sub.2           1        0.76                                               (g/10 minutes)                                                                I.sub.10 /I.sub.2 7.61     8.7                                                PI (kpoise)       14       15                                                 Melt tension (gms)                                                                              1.46     1.39                                               Elastic modulus at 0.1                                                                          1481     1921                                               rad/sec                                                                       (dynes/cm.sup.2)                                                              OGMF*, critical shear rate                                                                      1186     652                                                (l/sec)                                                                       OGMF*, critical shear stress                                                                    0.431    0.323                                              (MPa)                                                                         OSMF**, critical shear rate                                                                     about 764                                                                              about 402                                          (l/sec)                                                                       OSMF**, critical shear stress                                                                   0.366    0.280                                              (MPa)                                                                         ______________________________________                                         *Onset of Gross Melt Fracture.                                                **Onset of Surface Melt Fracture.                                        

The onset of gross melt fracture can easily be identified from the shearstress vs. shear rate plot shown in FIG. 4 where a sudden increase ofshear rate occurs at an apparent shear stress of about 3.23×10⁶ dyne/cm²(0.323 MPa). A comparison of the critical shear stresses andcorresponding critical shear rates at the onset of gross melt fractureis listed in Table IV. The PI of Example 6 is surprisingly about thesame as Comparative Example 9, even though the I₁₀ /I₂ is lower forExample 6. The onset of melt fracture or sharkskin for Example 6 is alsoat a significantly higher shear stress and shear rate in comparison withthe Comparative Example 9. Furthermore, it is also unexpected that theMelt Tension (MT) of Example 6 is higher than that of ComparativeExample 9, even though the melt index for Example 6 is slightly higherand the I₁₀ /I₂ is slightly lower than that of Comparative Example 9.

COMPARATIVE EXAMPLES 10-19

Batch ethylene/1-octene polymerizations were conducted under thefollowing conditions:

    Preparation of  HNEt.sub.3 !+ MeB(C.sub.6 F.sub.5).sub.3 !

A 100 ml flask was charged with 1.00 gram oftris(pentafluorophenyl)boron (1.95 mmol) and 70 ml of anhydrous pentane.After dissolution, 1.5 ml of MeLi (1.4M in diethyl ether, 2.1 mmol, 1.07equiv) was added at 25 C. via syringe. A milky white mixture formedimmediately and, after several minutes, two phases formed. The mixturewas stirred for 15 hr and then the upper layer decanted. The viscouslower layer was washed twice with 30 ml of pentane and concentrated invacuo for 2 hours to give a clear, colorless, viscous oil. Undernitrogen, the oil was quenched with a 40 ml of an aqueous 0.5M HNEt₃ Clsolution (20 mmol, 10 equiv) which had previously been cooled to 0 C. Awhite, gooey precipitate formed instantly. After two minutes, the solidwas collected by filtration and washed twice with 20 ml of 0.5M HNEt₃ Clsolution followed by two washings with distilled water. The solid wasdehydrated under high vacuum at 25 C. for 15 hours to give a powderywhite solid (0.77 grams, 63%) which was identified as the desiredtriethylammonium tris(pentafluorophenyl)methylborate salt

Preparation of HNEt₃ !+ (allyl)B(C₆ F₅)3!-

A 100 ml flask was charged with 1.00 gram oftris(pentafluorophenyl)boron (1.95 mmol) and 40 ml of anhydrous pentane.After dissolution, 2.05 ml of (allyl)MgBr (1.0M in diethyl ether, 2.05mmol, 1.05 equiv) was added at 25 C. via syringe. A cloudy white mixtureformed immediately and, after several minutes, two phases formed. Themixture was stirred for 15 hr and then the upper layer decanted. Theviscous lower layer was washed twice with 30 ml of pentane andconcentrated in vacuo for 2 hours to give a clear, colorless, viscousoil. Under nitrogen, the oil was quenched with a 40 ml of an aqueous0.5M HNEt₃ Cl solution (20 mmol 10 equiv) which had previously beencooled to 0 C. A gooey, white precipitate formed after several minutes.The solid was collected by filtration and washed twice with 20 ml of0.5M HNEt₃ Cl solution followed by two washings with distilled water.The solid was dehydrated under high vacuum at 25 C. for 15 hours to givea pasty white solid (0.39 grams, 30%) which was identified as thedesired triethylammonium tris(pentafluorophenyl)allylborate salt

Batch Reactor Polymerization Procedure

A 2 L stirred autoclave was charged with the desired amounts of a mixedalkane solvent (Isopar® E, available from Exxon Chemicals, Inc.) and1-octene comonomer. The reactor was heated to the polymerizationtemperature. Hydrogen was added by differential pressure expansion froma 75 ml addition tank.

The term "hydrogen delta psi" in Table 1 represents the difference inpressure between the starting and final pressure in the hydrogenaddition tank after adding hydrogen to the 2 L reactor containing atotal of approximately 1200 ml of solvent and 1-octene. The reactor washeated to the polymerization temperature and was saturated with ethyleneto the desired pressure. For these experiments, a constantethylene/solvent pressure of about 500 psig at a temperature of 140 C.corresponds to an ethylene concentration of about 8.4 percent by weightof the reactor contents. Metal complex and cocatalyst were mixed in adrybox by syringing the desired amount of 0.0050M metal complex solution(in Isopar® E or toluene) into a solution of the cocatalyst (in Isopar®E or toluene). This solution was then transferred to a catalyst additiontank and injected into the reactor. The polymerization was allowed toproceed for the desired time and then the solution was drained from thebottom of the reactor and quenched with isopropanol. About 100 mg of ahindered phenolic antioxidant (Irganox® 1010, available from Ciba-Geigycorporation) was added and the polymer was air dried overnight. Theresidual solvent was removed in a vacuum oven overnight. The results areshown in Table V and VA:

                  TABLE V                                                         ______________________________________                                        Comp. H.sub.2 1-octene Isopar                                                                              yield                                                                              Effcny. Aluminum                            Ex.   () psi) (gms)    E (gms)                                                                             (gms)                                                                              (gm/gm Ti)                                                                            (ppm)                               ______________________________________                                        10A*  50      38       820  39.6  330,689 0                                   11A*  25      38       820  70.1  390,257 0                                   12A*  35      38       820  46.4  258,316 0                                   13A*  30      38       820  48.8  271,677 0                                   14A*  35      30       828  52.1  290,049 0                                   15A*  27      38       820  36.5  152,401 0                                   16A** 26      38       820  47.8  266,l10 0                                   17B***                                                                              35      40       818  19.7   41,127 6850                                18B***                                                                              50      40       818  19.7   41,127 6850                                19B***                                                                              25      40       818  18.3   38,204 7380                                ______________________________________                                         A = metal complex of  (C.sub.5 Me.sub.4)SiMe.sub.2 N(tBu)! TiMe.sub.2 (as     in U.S. Pat. No. 5,064,802)                                                   B = metal complex of  (C.sub.5 Me.sub.4)SiMe.sub.2 N(tBu)! TiCl.sub.2 (as     in U.S. Pat. No. 5,026,798)                                                   * = Cocatalyst of  Et.sub.3 NH! +  (allyl)B(C.sub.6 F.sub.5).sub.3 !-- (a     in U.S. Pat. No. '802)                                                        ** = Cocatalyst of  Et.sub.3 NH! +  (Me)B(C.sub.6 F.sub.5).sub.3)-- (as i     U.S. Pat. No. '802)                                                           *** = methyl aluminoxane (MAO) (as in U.S. Pat. No. '798)                     Reactor temperature is constant at about 140 C.                               Ethylene/solvent pressure is constant at about 500 psig                       Run time is about 15 minutes                                             

                  TABLE VA                                                        ______________________________________                                                 μmoles    μmoles                                                                              Irganox 1010                                   Comp. Ex.                                                                              complex      cocatalyst                                                                             (ppm)                                          ______________________________________                                        10A*     2.5          2.5      2500                                           11A*     3.75         3.75     1400                                           12A*     3.75         3.75     2200                                           13A*     3.75         3.75     2000                                           14A*     3.75         3.75     1900                                           15A*     5            5        2700                                           16A*     3.75         3.75     2000                                           17B***   10           5000     5000                                           18B***   10           5000     5000                                           19B***   10           5000     5500                                           ______________________________________                                         A = metal complex of  (C.sub.5 Me.sub.4)SiMe.sub.2 N(tBu)! TiMe.sub.2 (as     in U.S. Pat. No. 5,064,802)                                                   B = metal complex of  (C.sub.5 Me.sub.4)SiMe.sub.2 N(tBu)! TiCl.sub.2 (as     in U.S. Pat. No. 5,026,798)                                                   * = Cocatalyst of  Et.sub.3 NH! +  (allyl)B(C.sub.6 F.sub.5).sub.3 !-- (a     in U.S. Pat. No. '802)                                                        ** = Cocatalyst of  Et.sub.3 NH! +  (Me)B(C.sub.6 F.sub.5).sub.3 !-- (as      in U.S. Pat. No. '802)                                                        *** = methyl aluminoxane (MAO) (as in U.S. Pat. No. '798)                     Reactor temperature is constant at about 140 C.                               Ethylene/solvent pressure is constant at about 500 psig                       Run time is about 15 minutes                                             

The samples were each extruded via a Gas Extrusion Rheometer (GER) at190 C. using 0.0296 inch diameter die (preferably 0.0143 inch diameterdie for high flow polymers, e.g. 50-100 MI or greater) having L/D of20:1 and entrance angle of 180 degrees, as shown in the attacheddrawing. The OGMF can easily be identified from the shear stress vs.shear rate plot where a sudden jump of shear rate occurs or when thesurface of the extrudate becomes very rough or irregular, or from deepridges which can be clearly detected by visual observation. OSMF ischaracterized by fine scale surface irregularities ranging from loss ofsurface gloss to the more severe form of matte or sharkskin which caneasily be seen using microscopy at a magnification of 40×.

Table VI displays the test results from Comparative Examples 10-19:

                  TABLE VI                                                        ______________________________________                                                                                  OGMF*                                     I.sub.2                      OGMF*  Shear                               Comp. (gm/           (I.sub.10 /I.sub.2) -                                                                Measured                                                                             Shear Rate                                                                           Stress                              Ex.   10 min) I.sub.10 /I.sub.2                                                                    4.63   M.sub.w /M.sub.n                                                                     (sec.sup.-1)                                                                         (MPa)                               ______________________________________                                        10    4.52    5.62   0.99   1.856  706    0.344                               11    0.67    6.39   1.76   1.834  118    0.323                               12    2.24    5.62   0.99   1.829  300    0.323                               13    2.86    5.60   0.97   1.722  397    0.323                               14    3.25    5.66   1.03   1.827  445    0.302                               15    1.31    5.67   1.04   1.718  227    0.302                               16    1.97    5.7    1.07   1.763  275    0.302                               17    0.36    12.98  8.35   5.934  <29    <0.086                              18    0.40    13.34  8.71   5.148  <11.08 <0.086                              19    0.13    13.25  8.62   6.824  <10.39 <0.086                              ______________________________________                                    

Comparative Examples 10-16 were prepared using the catalyst compositionas described in U.S. Pat. No. 5,064,802 (Stevens et al.) as describedabove. Comparative Examples 17-19 were prepared using the catalystcomposition described in U.S. Pat. No. 5,026,798 (Canich), as describedabove. All of the Comparative Polymer Examples made using a batchreactor at an ethylene concentration of about 8.4 percent by weight ofthe reactor contents or more tested had onset of gross melt fracture ata shear stress of less than or equal to 0.344 MPa (3.44×10₆ dyne/cm²).

Interestingly, an ethylene concentration of about 8.4 percent isconsidered to be on the low side for a batch polymerization procedure,since it limits the reaction kinetics and slows the polymerizationprocess. Increasing the ethylene concentration in a batch reactor, as istaught in U.S. Pat. No. 5,026,798 (Canich), where the calculatedpropylene reactor concentrations for these ten examples ranges from alow of about 12.6 percent (Example 1) to a high of about 79 percent(Example 6), by weight of the reactor contents, results inpolymerization of polymers which do not have the novel structurediscovered by Applicants, as the OGMF data in Table VI demonstrates.Furthermore, the I₁₀ /I₂ ratio of such comparative polymers made using abatch reactor at relatively high ethylene concentrations increases asthe molecular weight distribution, M_(w) /M_(n), increases, as isexpected based on conventional Ziegler polymerized polymers.

EXAMPLE 20 AND COMPARATIVE EXAMPLE 21

Blown film is fabricated from the two novel ethylene/1-octene polymersof Examples 5 and 6 made in accordance with the present invention andfrom two comparative conventional polymers made according toconventional Ziegler catalysis. The blown films are tested for physicalproperties, including heat seal strength versus heat seal temperature(shown in FIG. 5 for Examples 20 and 22 and Comparative Examples 21 and23), machine (MD) and cross direction (CD) properties (e.g., tensileyield and break, elongation at break and Young's modulus). Other filmproperties such as dart, puncture, tear, clarity, haze, 20 degree glossand block are also tested.

Blown Film Fabrication Conditions

The improved processing substantially linear polymers of the presentinvention produced via the procedure described earlier, as well as twocomparative resins are fabricated on an Egan blown film line using thefollowing fabrication conditions:

2 inch (5 cm) diameter extruder

3 inch (7.6 cm) die

30 mil die gap

25 RPM extruder speed

460 F. (238 C.) melt temperature

1 mil gauge

2.7:1 Blow up ratio (12.5 inches (31.7 cm) layflat)

12.5 inches (31.7 cm) frost line height

The melt temperature is kept constant by changing the extrudertemperature profile. Frost line height is maintained at 12.5 inches(31.7 cm) by adjusting the cooling air flow. The extruder output rate,back pressure and power consumption in amps are monitored throughout theexperiment The polymers of the present invention and the comparativepolymers are all ethylene/1-octene copolymers. Table VII summarizesphysical properties of the two polymers of the invention and for the twocomparative polymers:

                  TABLE VII                                                       ______________________________________                                                          Comparative        Comparative                              Property                                                                             Example 20 Example 21                                                                              Example 22                                                                             Example 23                               ______________________________________                                        I.sub.2 (10                                                                          1          1         1        0.8                                      minutes)                                                                      Density                                                                              0.92       0.92      0.902    0.905                                    (g/cm.sup.3)                                                                  I.sub.10 /I.sub.2                                                                    9.45       about 8   7.61     8.7                                      M.sub.w /M.sub.n                                                                     1.97       about 4   2.09     about 5                                  ______________________________________                                    

Tables VIII and IX summarize the film properties measured for blown filmmade from two of these four polymers:

                  TABLE VIII                                                      ______________________________________                                        Blown film properties                                                                                     Comparative                                                                            Comparative                                       Example   Example  Example  Example                                  Property 20 MD     20 CD    21 MD    21 CD                                    ______________________________________                                        Tensile yield                                                                            1391      1340     1509     1593                                   (psi)                                                                         Tensile break                                                                            7194      5861     6698     6854                                   (psi)                                                                         Elongation                                                                               650       668      631      723                                    (percent)                                                                     Young's  18,990    19,997   23,086   23,524                                   modulus (psi)                                                                 PPT* tear                                                                              5.9       6.8      6.4      6.5                                      (gms)                                                                         ______________________________________                                         *Puncture Propagation Tear                                                    MD = machine direction                                                        CD = cross direction                                                     

                  TABLE IX                                                        ______________________________________                                                                    Comparative                                       Property          Example 20                                                                              Example 21                                        ______________________________________                                        Dart A (grams)    472       454                                               Puncture (grams)  235       275                                               Clarity (percent transmittance)                                                                 71        68                                                Haze (percent)    3.1       6.4                                               20 degree gloss   114       81                                                Block (grams)     148       134                                               ______________________________________                                    

During the blown film fabrication, it is noticed that at the same screwspeed (25 rpm) and at the same temperature profile, the extruder backpressure is about 3500 psi at about 58 amps power consumption forComparative Example 21 and about 2550 psi at about 48 amps powerconsumption for Example 20, thus showing the novel polymer of Example 20to have improved processability over that of a conventionalheterogeneous Ziegler polymerized polymer. The throughput is also higherfor Example 20 than for Comparative Example 21 at the same screw speed.Thus, Example 20 has higher pumping efficiency than Comparative Example21 (i.e., more polymer goes through per turn of the screw).

As FIG. 5 shows, the heat seal properties of polymers of the presentinvention are improved, as evidenced by lower heat seal initiationtemperatures and higher heat seal strengths at a given temperature, ascompared with conventional heterogeneous polymers at about the same meltindex and density.

EXAMPLES 24 AND 25

The polymer products of Examples 24 and 25 are produced in a continuoussolution polymerization process using a continuously stirred reactor, asdescribed in copending U.S. Pat. No. 5,272,236. The metal complex C₅ Me₄(SiMe₂ N^(t) Bu)!TiMe₂ is prepared as described in U.S. Pat. No.5,272,236 and the cocatalysts used are tris(pentafluorophenyl) borane(B:Ti ratio of 2:1) and MMAO (Al:Ti ratio of 4:1). For Example 24 theethylene concentration in the reactor is about 1.10 percent and forExample 25 the ethylene concentration in the reactor is about 1.02percent (percentages based on the weight of the reactor contents). Foreach Example, the reactor is run without hydrogen.

Additives (e.g., antioxidants, pigments, etc.) can be incorporated intothe interpolymer products either during the pelletization step or aftermanufacture, with a subsequent re-extrusion. Examples 24 and 25 are eachstabilized with 1250 ppm Calcium Stearate, 200 ppm Irganox™ 1010, and1600 ppm Irgafos™ 168. Irgafos™ 168 is a phosphite stabilizer andIrganox™ 1010 is a hindered polyphenol stabilizer (e.g., tetrakismethylene 3-(3,5-ditertbutyl-4-hydroxyphenylpropionate)!methane. Bothare trademarks of and made by Ciba-Geigy Corporation.

EXAMPLE 24 AND COMPARATIVE EXAMPLE 26

Example 24 is an ethylene/1-octene elastic substantially linear ethylenepolymer produced as described herein.

Comparative Example 26 is an ethylene/1-butene copolymer trademarkedExact™ made by Exxon Chemical containing butylated hydroxy toluene (BHT)and Irganox™ 1076 as polymeric stabilizers. Table X summarizes physicalproperties and rheological performance of Example 24 and ComparativeExample 26:

                  TABLE X                                                         ______________________________________                                                                     Comparative                                      Property           Example 24                                                                              Example 26                                       ______________________________________                                        I.sub.2 (g/10 minutes)                                                                           3.3       3.58                                             Density (g/cm.sup.3)                                                                             0.870     0.878                                            I.sub.10 /I.sub.2  7.61      5.8                                              M.sub.w /M.sub.n   1.97      1.95                                             PI (kPoise)        3.2       8.4                                              Elastic Modulus @ 0.1 rad/sec                                                                    87.7      8.3                                              (dyne/cm.sup.2)                                                               OSMF*, critical shear rate                                                                       660       250                                              (sec.sup.-1)                                                                  ______________________________________                                         *Onset of surface melt fracture                                          

Even though Example 24 and Comparative Example 26 have very similarmolecular weight distributions (M_(w) /M_(n)), I₂ and density, Example24 has a much lower processing index (PI) (38 percent of the PI ofComparative Example 26), a much higher shear rate at the onset ofsurface melt fracture (264 percent of shear rate at onset of OSMF) andan elastic modulus an order of magnitude higher than Comparative Example26, demonstrating that Example 24 has much better processability andhigher melt elasticity than Comparative Example 26.

Elastic modulus is indicative of a polymer's melt stability, e.g., morestable bubbles when making blown film and less neck-in during meltextrusion. Resultant physical properties of the finished film are alsohigher.

Onset of surface melt fracture is easily identified by visuallyobserving the surface extrudate and noting when the extrudate startslosing gloss and small surface roughness is detected by using 40×magnification.

Dynamic shear viscosity of the polymers is also used to show differencesbetween the polymers and measures viscosity change versus shear rate. ARheometrics Mechanical Spectrometer (Model RMS 800) is used to measureviscosity as a function of shear rate. The RMS 800 is used at 190 C. at15 percent strain and a frequency sweep (i.e., from 0.1-100 rad/sec)under a nitrogen purge. The parallel plates are positioned such thatthey have a gap of about 1.5-2 mm. Data for Example 24 and ComparativeExample 26 are listed in Table XI and graphically displayed in FIG. 6.

                  TABLE XI                                                        ______________________________________                                                                 Dynamic Viscosity                                    Shear Rate                                                                            Dynamic Viscosity (poise)                                                                      (poise) for Comparative                              (rad/sec)                                                                             for Example 24   Example 26                                           ______________________________________                                        0.1     28290            18990                                                0.1585  28070            18870                                                0.2512  27630            18950                                                0.3981  27140            18870                                                0.631   26450            18840                                                1       25560            18800                                                1.585   24440            18690                                                2.512   23140            18540                                                3.981   21700            18310                                                6.31    20170            17960                                                10      18530            17440                                                15.85   16790            16660                                                25.12   14960            15620                                                39.81   13070            14310                                                63.1    11180            12750                                                100      9280            10960                                                ______________________________________                                    

Surprisingly, Example 24 shows a shear thinning behaviour, even thoughExample 24 has a narrow molecular weight distribution. In contrast,Comparative Example 26 shows the expected behaviour of a narrowmolecular weight distribution polymer, with a flatter viscosity/shearrate curve.

Thus, elastic substantially linear ethylene polymers made in accordancewith the present invention (e.g. Example 24) have lower melt viscositythan a typical narrow molecular weight distribution linear copolymermade by single site catalyst technology at the melt processing shearrate region of commercial interest. In addition, the novel elasticsubstantially linear ethylene polymers have a higher low shear/zeroshear viscosity than the Comparative linear polymer, thus demonstratingthat the copolymers of the invention have higher "green strength" whichis useful for forming and maintaining blended compositions such as thoseused in the wire and cable coating industry, where the compoundedmaterials must maintain their integrity at low or zero shear withoutsegregating the components.

EXAMPLE 25 AND COMPARATIVE EXAMPLE 27

Example 25 is an ethylene/1-octene elastic substantially linear ethylenepolymer produced in a continuous solution polymerization process asdescribed herein.

Comparative Example 27 is an ethylene/propene copolymer made by MitsuiPetroChemical Corporation and trademarked Tafmer™ P-0480. Table XIIsummarizes physical properties and rheological performance of these twopolymers:

                  TABLE XII                                                       ______________________________________                                                                   Comparative                                        Property         Example 25                                                                              Example 27                                         ______________________________________                                        I.sub.2 (g/10 minutes)                                                                         1.01      1.1                                                Density (g/cm.sup.3)                                                                           0.870     0.870                                              I.sub.10 /I.sub.2                                                                              7.62      6.06                                               M.sub.w /M.sub.n 1.98      1.90                                               PI (kPoise)      7.9       27.4                                               Elastic Modulus @ 0.1                                                                          964       567.7                                              rad/sec (dyne/cm.sup.2)                                                       OSMF*, critical shear rate                                                                     781       105                                                (sec.sup.-1)                                                                  ______________________________________                                         *Onset of surface melt fracture                                          

Even though Example 25 and Comparative Example 27 have similarly narrowmolecular weight distributions (M_(w) /M_(n)), I₂, and density, Example25 has a PI which is 28 percent of that of Comparative Example 27, a 743percent of the shear rate at the onset of surface melt fracture and ahigher elastic modulus than Comparative Example 27, demonstrating thatExample 24 has much better processability than Comparative Example 27.Onset of surface melt fracture is easily identified by visuallyobserving the surface extrudate and noting when the extrudate startslosing gloss and small surface roughness is detected by using 40×magnification.

EXAMPLES 28-37

Examples 28-35 are ethylene/propene copolymers made using theconstrained geometry catalyst described herein and in a continuoussolution polymerization process. Examples 36 and 37 areethylene/1-butene copolymers made using the constrained geometrycatalyst described herein and in a continuous solution polymerizationprocess. Examples 28-37 each contained approximately 1250 ppm calciumstrearate, 200 ppm Irganox 1010. These polymers did not, however,contain a secondary antioxidant (e.g. a phosphite). The low level ofphenol (i.e. 200 ppm Irganox 1010) coupled with the lack of thesecondary antioxidant may have contributed to the lower melt fractureperformance of some of the polymers shown in Table XV. It is well knownthat thermally processing polyethylene polymers, especially in thepresence of oxygen, can lead to oxidative crosslinking and extrusionvariation, i.e. melt fracture. Table XIII and XIIIA describe thepolymerization conditions and Table XIV describes the resultant polymerphysical properties for Examples 28-35:

                  TABLE XIII                                                      ______________________________________                                            Reactor     Estimated reactor                                                                         Ethylene                                                                              Hydrogen/                                     ethylene conc.                                                                            PE conc.    flow    ethylene ratio                            Ex. (weight percent)                                                                          (weight percent)                                                                          rate (lbs/hr)                                                                         (mole percent)                            ______________________________________                                        28  5.3         6.0         3.19    0.048                                     29  4.2         7.3         3.19    0.024                                     30  4.0         8.9         3.19    0.028                                     31  3.5         9.3         3.18    0.024                                     32  2.5         10.6        3.20    0.027                                     33  2.6         10.7        3.18    0.007                                     34  1.3         10.5        3.19    0.027                                     35  1.0         10.9        3.19    0.010                                     ______________________________________                                    

                  TABLE XIIIA                                                     ______________________________________                                             Reactor   Ethylene    Diluent/ Comonomer/                                Ex.  temp (C.) Conversion %                                                                              ethylene ratio                                                                         olefin ratio*                             ______________________________________                                        28   170       51          8.2      25.5                                      29   172       61          8.1      24.0                                      30   171       67          7.1      16.6                                      31   171       71          7.2      20.1                                      32   170       79          7.1      15.6                                      33   173       78          7.1      16.7                                      34   145       88          8.2      17.8                                      35   158       91          8.2      18.8                                      ______________________________________                                         *Comonomer/total olefin ratio = percentage weight ratio of                    propene/(propene + ethylene).                                            

                  TABLE XIV                                                       ______________________________________                                                I.sub.2 (gms/10     Density                                           Ex.     minutes) I.sub.10 /I.sub.2                                                                        (gm/cm.sup.3)                                                                        M.sub.w /M.sub.n                           ______________________________________                                        28      1.08     7.8        0.9176 2.00                                       29      1.02     8.8        0.9173 2.17                                       30      0.82     9.2        0.9175 2.08                                       31      0.79     9.4        0.9196 2.04                                       32      1.01     10.6       0.9217 2.09                                       33      0.83     12.4       0.9174 2.31                                       34      0.54     15.2       0.9201 2.12                                       35      0.62     15.6       0.9185 2.32                                       ______________________________________                                    

FIG. 7 graphically displays a best fit line drawn through a plot of theI₁₀ /I₂ ratio for the ethylene/propene substantially linear polymers ofExamples 28-35 as a function of ethylene concentration in thepolymerization reactor. Surprisingly, in contrast to conventionalZiegler polymerized polymers and in contrast to a batch polymerizationusing the same catalyst and relatively high ethylene concentrations, asthe ethylene concentration in the reactor decreases using a continouspolymerization process, the I₁₀ /I₂ ratio (indicating the amount of longchain branching the novel substantially linear polymers) increases, eventhough the molecular weight distribution, M_(w) /M_(n), remains verynarrow and essentially constant at about 2.

Table 15 shows the critical shear stress and critical shear rate at OGMFand OSMF for Examples 28-35:

                  TABLE XV                                                        ______________________________________                                        Example    OSMF         OGMF                                                  ______________________________________                                        28 (shear stress)                                                                        2.15 × 10.sup.6 dyne/cm.sup.2                                                        4.09 × 10.sup.6 dyne/cm.sup.2                   28 (shear rate)                                                                          129.8 sec.sup.-1                                                                           668.34 sec.sup.-1                                     29 (shear stress)                                                                        1.94 × 10.sup.6 dyne/cm.sup.2                                                        4.3 × 10.sup.6 dyne/cm.sup.2                    29 (shear rate)                                                                          118.8 sec.sup.-1                                                                           652.1 sec.sup.-1                                      30 (shear stress)                                                                        1.08 × 10.sup.6 dyne/cm.sup.2                                                        4.3 × 10.sup.6 dyne/cm.sup.2                    30 (shear rate)                                                                          86.12 sec.sup.-1                                                                           650.7 sec.sup.-1                                      31 (shear stress)                                                                        1.08 × 10.sup.6 dyne/cm.sup.2                                                        >4.3 × 10.sup.6 dyne/cm.sup.2                   31 (shear rate)                                                                          90.45 sec.sup.-1                                                                           >6.83 sec.sup.-1                                      32 (shear stress)                                                                        1.94 × 10.sup.6 dyne/cm.sup.2                                                        3.66 × 10.sup.6 dyne/cm.sup.2                   32 (shear rate)                                                                          178.2 sec.sup.-1                                                                           673 sec.sup.-1                                        33 (shear stress)                                                                        2.15 × 10.sup.6 dyne/cm.sup.2                                                        about 3.23 × 10.sup.6 dyne/cm.sup.2             33 (shear rate)                                                                          235.7 sec.sup.-1                                                                           about 591 sec.sup.-1                                  34 (shear stress)                                                                        1.94 × 10.sup.6 dyne/cm.sup.2                                                        3.44 × 10.sup.6 dyne/cm.sup.2                   34 (shear rate)                                                                          204.13 sec.sup.-1                                                                          725.23 sec.sup.-1                                     35 (shear stress)                                                                        1.94 × 10.sup.6 dyne/cm.sup.2                                                        about 3.26 × 10.sup.6 dyne/cm.sup.2             35 (shear rate)                                                                          274.46 sec.sup.-1                                                                          637.7 sec.sup.-1                                      ______________________________________                                    

Table XVI and XVIA describe the polymerization conditions and Table XVIIdescribes the resultant polymer physical properties forethylene/1-butene copolymer Examples 36 and 37:

                  TABLE XVI                                                       ______________________________________                                            Reactor     Reactor     Ethylene                                                                              Hydrogen/                                     ethylene conc.                                                                            PE conc     flow    ethylene ratio                            Ex. (weight percent)                                                                          (weight percent)                                                                          rate (lbs/hr)                                                                         (mole percent)                            ______________________________________                                        36  5.3         5.8         3.20    0.035                                     37  1.3         10.8        3.19    0.010                                     ______________________________________                                    

                  TABLE XVIA                                                      ______________________________________                                             Reactor   Diluent/    Ethylene Comonomer/                                Ex.  temp (C.) Ethylene Ratio                                                                            Conversion (%)                                                                         olefin ratio*                             ______________________________________                                        36   170       8.1         51       24.2                                      37   152       8.2         87       17.1                                      ______________________________________                                         *Comonomer/total olefin ratio = percentage weight ratio of                    1butene/(1-butene + ethylene).                                           

                  TABLE XVII                                                      ______________________________________                                               I.sub.2               Density                                          Ex.    (gms/10 minutes)                                                                          I.sub.10 /I.sub.2                                                                       (gm/cm.sup.3)                                                                        M.sub.w /M.sub.n                          ______________________________________                                        36     0.59        7.5       0.9201 2.66                                      37     1.03        11.4      0.9146 2.22                                      ______________________________________                                    

The data in Tables XVI, XVIA and XVII show that as the ethyleneconcentration in the reactor decreases while using the constrainedgeometry catalyst as described herein, the I₁₀ /I₂ ratio of the novelsubstantially linear polymers increases, indicating the amount of longchain branching in the novel polymers, even while the molecular weightdistribution, M_(w) /M_(n), of the novel polymers remains narrow atessentially about 2.

Table XVIII shows the critical shear stress and critical shear rate atOGMF and OSMF for Examples 36 and 37:

                  TABLE XVIII                                                     ______________________________________                                        Example      OSMF          OGMF                                               ______________________________________                                        36 (shear stress)                                                                          1.94 × 10.sup.6 dyne/cm.sup.2                                                         4.09 × 10.sup.6 dyne/cm.sup.2                36 (shear rate)                                                                            52.3 sec.sup.-1                                                                             234.45 sec.sup.-1                                  37 (shear stress)                                                                          1.08 × 10.sup.6 dyne/cm.sup.2                                                         3.01 × 10.sup.6 dyne/cm.sup.2                37 (shear rate)                                                                            160.5 sec.sup.-1                                                                            493.9 sec.sup.-1                                   ______________________________________                                    

COMPARATIVE EXAMPLE 38

An ethylene polymer, as described in U.S. Pat. No. 5,218,071, ispolymerized according to the teachings of that patent and tested formelt fracture properties.

All catalyst manipulations were performed under anhydrous, anaerobicconditions in an inert atmosphere box. The solvents, toluene and IsoparE, and the comonomer, octene-1, were thoroughly dried and deaeratedbefore use. poly(methylalumioxane) (PMAO) was obtained from AKZOChemicals Inc. as a 1.55M Al in toluene solution and used as received.The metallocene ethylenebis(indenyl)hafnium dichloride was obtained fromSchering A.G. as a solid. This metallocene is known to contain 0.2weight percent Zirconium contamination. A slurry of the hafnium complexwas prepared from this solid (0.253 g; 0.5 mmol; 0.010M) and 50 mLtoluene. The slurry was thoroughly stirred overnight prior to use.

A one gallon, stirred autoclave reactor was charged with Isopar E (2.1L) and octene-1 (175 mL) and the contents heated to 80 C. Upon reachingtemperature, a sample of the PMAO (26.8 mL; 40.0 mmol Al) in toluene waspressured into the reactor from a 75 mL cylinder using a nitrogen flush.After a few minutes, an aliquot of the metallocene slurry (4.0 mL; 0.040mmol; Al:Hf=1000:1) was flushed into the reactor in a similar manner.Ethylene was continuously supplied to the reactor at a rate of 17 g/minto initiate polymerization. The ethylene flow was maintained for tenminutes and during the latter part of the polymerization the flow rateslowed as the pressure approached a setpoint of 100 psig. After thistime, the ethylene supply was shut off and the contents of the reactortransferred by pressure to a glass resin kettle containing a smallamount of antioxidant (0.30 g Irgaphos 168; 0.07 g Irganox 1010). Thesolvent was slowly allowed to evaporate and the polymer obtained formthe solution was dried under vacuum at 50 C. for 72 h. The yield of theproduct was 159 g or an efficiency of 3975 g PE/mmol Hf.

The recovered polymer had a M_(w) =1.341×10⁵, M_(n) =5.65×10₄, M_(w)/M_(n) =2.373, density (measured in a gradien column)=0.8745 g/cc, I₂=0.63 g/10 min., I₁₀ /I₂ =15.9, and had two distinct melting peaks (asshown in FIG. 8). The polymer showed two peak melting points, one at30.56 C. and the other at 102.55 C. The polymer also showed two peakcrystallization points, one at 9.47 C. and the other at 81.61 C.

Melt fracture was determined using the GER at 190 C. with a die having adiameter of 0.0145 inches and an L/D=20.

We claim:
 1. A composition comprising an ethylene polymer and at leastone other natural or synthetic polymer, wherein the ethylene polymer ischaracterized as having:a) a melt flow ratio, I₁₀ /I₂, ≧5.63, b) amolecular weight distribution, M_(w) /M_(n), defined by the equation:

    M.sub.w /M.sub.n ≦(I.sub.10 /I.sub.2)-4.63, and

c) a critical shear stress at onset of gross melt fracture greater thanabout 4×10⁶ dyne/cm², d) a single melting point as determined bydifferential scanning calorimetry between -30 C. and 150 C. and e) lessthan about 20 ppm aluminum.
 2. A composition comprising an ethylenepolymer and at least one other natural or synthetic polymer, wherein theethylene polymer is characterized as:(A) an ethylene/alpha-olefinsubstantially linear ethylene polymer, or (B) a substantially linearethylene homopolymer.
 3. The composition of claim 2 wherein thesynthetic polymer is a conventional Ziegler polymerizedethylene/alpha-olefin polymer.
 4. A composition comprising an ethylenepolymer and at least one other natural or synthetic polymer, wherein theethylene polymer is characterized as having:a) a melt flow ratio, I₁₀/I₂, ≧5.63, b) a molecular weight distribution, M_(w) /M_(n), defined bythe equation:

    M.sub.w /M.sub.n ≦(I.sub.10 /I.sub.2)-4.63, and

c) a critical shear rate at onset of surface melt fracture at least 50percent greater than the critical shear rate at the onset of surfacemelt fracture of a linear ethylene polymer having an I₂, M_(w) /M_(n)and density within ten percent of the ethylene polymer, d) a singlemelting point as determined by differential scanning calorimetry between-30 C. and 150 C., and e) less than about 20 ppm aluminum.
 5. Acomposition comprising an ethylene polymer and at least one othernatural or synthetic polymer, wherein the ethylene polymer ischaracterized as having:a) a melt flow ratio, I₁₀ /I₂, ≧7 b) a molecularweight distribution, M_(w) /M_(n) of from about 1.5 to about 2.5, c) asingle melting peak as determined by differential scanning calorimetrybetween -30 C. and 150 C., and d) less than about 20 ppm aluminum.
 6. Acomposition comprising an ethylene polymer and at least one othernatural or synthetic polymer, wherein the ethylene polymer ischaracterized as having:a) a melt flow ratio, I₁₀ /I₂, ≦5.63, b) amolecular weight distribution, M_(w) /M_(n) of from about 1.5 to about2.5, c) a critical shear rate at onset of surface melt fracture of atleast 50 percent greater than the critical shear rate at the onset ofsurface melt fracture of a linear ethylene polymer having an I₂, M_(w)/M_(n) and density within ten percent of the ethylene polymer, d) asingle melting point as determined by differential scanning calorimetrybetween -30 C. and 150 C., and e) less than about 20 ppm aluminum.
 7. Acomposition comprising an ethylene polymer and at least one othernatural or synthetic polymer, wherein the ethylene polymer ischaracterized as having (i) a critical shear rate at onset of surfacemelt fracture of at least 50 percent greater than the critical shearrate at the onset of surface melt fracture of a linear ethylene polymerhaving an I₂, M_(w) /M_(n) and density within ten percent of theethylene polymer, (ii) a single melting point as determined bydifferential scanning calorimetry between -30 C. and 150 C., and (iii)less than about 20 ppm aluminum.
 8. A composition comprising an ethylenepolymer and at least one other natural or synthetic polymer, wherein theethylene polymer is characterized as a substantially linear ethylenepolymer having:a) from about 0.01 to about 3 long chain branches/1000total carbons, b) a critical shear stress at onset of gross meltfracture of greater than about 4×10⁶ dyne/cm², c) a single melting pointas determined by differential scanning calorimetry between -30 C. and150 C., and d) less than about 20 ppm aluminum.
 9. A compositioncomprising an ethylene polymer and at least one other natural orsynthetic polymer, wherein the ethylene polymer is characterized as asubstantially linear ethylene polymer having:a) from about 0.01 to about3 long chain branches/1000 total carbons, b) a critical shear stress atonset of surface melt fracture of at least 50 percent greater than thecritical shear rate at the onset of surface melt fracture of a linearethylene polymer having an I₂, M_(w) /M_(n) and density within tenpercent of the ethylene polymer, c) a single melting point as determinedby differential scanning calorimetry between -30 C. and 150 C., and d)less than about 20 ppm aluminum.
 10. A composition comprising anethylene polymer and at least one other natural or synthetic polymer,wherein the ethylene polymer is characterized as a substantially linearethylene polymer having:a) from about 0.01 to about 3 long chainbranches/1000 total carbons, b) a melt flow ratio, I₁₀ /I₂, ≧5.63, c) amolecular weight distribution, M_(w) /M_(n) from about 1.5 to about 2.5,d) a single melting point as determined by differential scanningcalorimetry between -30 C. and 150 C. and e) less than about 20 ppmaluminum.